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Quantum decoherence

Quantum decoherence is the loss of quantum coherence. Quantum decoherence has been studied to understand how quantum systems convert to systems which can be explained by classical mechanics. Beginning out of attempts to extend the understanding of quantum mechanics, the theory has developed in several directions and experimental studies have confirmed some of the key issues. Quantum computing relies on quantum coherence and is one of the primary practical applications of the concept.

Concept
In quantum mechanics, particles such as electrons are described by a wave function, a mathematical representation of the quantum state of a system; a probabilistic interpretation of the wave function is used to explain various quantum effects. As long as there exists a definite phase relation between different states, the system is said to be coherent. A definite phase relationship is necessary to perform quantum computing on quantum information encoded in quantum states. Coherence is preserved under the laws of quantum physics.

If a quantum system were perfectly isolated, it would maintain coherence indefinitely, but it would be impossible to manipulate or investigate it. If it is not perfectly isolated, for example during a measurement, coherence is shared with the environment and appears to be lost with time ─ a process called quantum decoherence or environmental decoherence. The quantum coherence is not lost but rather mixed with many more degrees of freedom in the environment, analogous to the way energy appears to be lost in by friction in classical mechanics when it actually has produced heat in the environment.

Decoherence can be viewed as the loss of information from a system into the environment (often modeled as a heat bath), since every system is loosely coupled with the energetic state of its surroundings. Viewed in isolation, the system's dynamics are non-unitary (although the combined system plus environment evolves in a unitary fashion). Thus the dynamics of the system alone are irreversible. As with any coupling, entanglements are generated between the system and environment. These have the effect of sharing quantum information with—or transferring it to—the surroundings.

Relation to interpretation of quantum mechanics
An interpretation of quantum mechanics is an attempt to explain how the mathematical theory of quantum physics might correspond to experienced reality. Decoherence calculations can be done in any interpretation of quantum mechanics, since those calculations are an application of the standard mathematical tools of quantum theory. However, the subject of decoherence has been closely related to the problem of interpretation throughout its history.

Decoherence has been used to understand the possibility of the collapse of the wave function in quantum mechanics. Decoherence does not generate actual wave-function collapse. It only provides a framework for apparent wave-function collapse, as the quantum nature of the system "leaks" into the environment. That is, components of the wave function are decoupled from a coherent system and acquire phases from their immediate surroundings. A total superposition of the global or universal wavefunction still exists (and remains coherent at the global level), but its ultimate fate remains an interpretational issue.

With respect to the measurement problem, decoherence provides an explanation for the transition of the system to a mixture of states that seem to correspond to those states observers perceive. Moreover, observation indicates that this mixture looks like a proper quantum ensemble in a measurement situation, as the measurements lead to the "realization" of precisely one state in the "ensemble".

The philosophical views of Werner Heisenberg and Niels Bohr have often been grouped together as the "Copenhagen interpretation", despite significant divergences between them on important points. In 1955, Heisenberg suggested that the interaction of a system with its surrounding environment would eliminate quantum interference effects. However, Heisenberg did not provide a detailed account of how this might transpire, nor did he make explicit the importance of entanglement in the process.

Origin of the concepts
Nevill Mott's solution to the iconic Mott problem in 1929 is considered in retrospect to be the first quantum decoherence work. It was cited by the first modern theoretical treatment.

Although he did not use the term, the concept of quantum decoherence was first introduced in 1951 by the American physicist David Bohm, who called it the "destruction of interference in the process of measurement". Bohm later used decoherence to handle the measurement process in the de Broglie-Bohm interpretation of quantum theory.

The significance of decoherence was further highlighted in 1970 by the German physicist H. Dieter Zeh, and it has been a subject of active research since the 1980s. Decoherence has been developed into a complete framework, but there is controversy as to whether it solves the measurement problem, as the founders of decoherence theory admit in their seminal papers.

The study of decoherence as a proper subject began in 1970, with H. Dieter Zeh's paper "On the Interpretation of Measurement in Quantum Theory". Zeh regarded the wavefunction as a physical entity, rather than a calculational device or a compendium of statistical information (as is typical for Copenhagen-type interpretations), and he proposed that it should evolve unitarily, in accord with the Schrödinger equation, at all times. Zeh was initially unaware of Hugh Everett III's earlier work, which also proposed a universal wavefunction evolving unitarily; he revised his paper to reference Everett after learning of Everett's "relative-state interpretation" through an article by Bryce DeWitt. (DeWitt was the one who termed Everett's proposal the many-worlds interpretation, by which name it is commonly known.) For Zeh, the question of how to interpret quantum mechanics was of key importance, and an interpretation along the lines of Everett's was the most natural. Partly because of a general disinterest among physicists for interpretational questions, Zeh's work remained comparatively neglected until the early 1980s, when two papers by Wojciech Zurek invigorated the subject. Unlike Zeh's publications, Zurek's articles were fairly agnostic about interpretation, focusing instead on specific problems of density-matrix dynamics. Zurek's interest in decoherence stemmed from furthering Bohr's analysis of the double-slit experiment in his reply to the Einstein–Podolsky–Rosen paradox, work he had undertaken with Bill Wootters, and he has since argued that decoherence brings a kind of rapprochement between Everettian and Copenhagen-type views.

Decoherence does not claim to provide a mechanism for some actual wave-function collapse; rather it puts forth a reasonable framework for the appearance of wave-function collapse. The quantum nature of the system is simply "leaked" into the environment so that a total superposition of the wave function still exists, but exists—at least for all practical purposes—beyond the realm of measurement. By definition, the claim that a merged but unmeasurable wave function still exists cannot be proven experimentally. Decoherence is needed to understand why a quantum system begins to obey classical probability rules after interacting with its environment (due to the suppression of the interference terms when applying Born's probability rules to the system).

Criticism of the adequacy of decoherence theory to solve the measurement problem has been expressed by Anthony Leggett.

Mechanisms
To examine how decoherence operates, an "intuitive" model is presented below. The model requires some familiarity with quantum theory basics. Analogies are made between visualizable classical phase spaces and Hilbert spaces. A more rigorous derivation in Dirac notation shows how decoherence destroys interference effects and the "quantum nature" of systems. Next, the density matrix approach is presented for perspective.

Phase-space picture
An N-particle system can be represented in non-relativistic quantum mechanics by a wave function $$\psi(x_1, x_2, \dots, x_N)$$, where each xi is a point in 3-dimensional space. This has analogies with the classical phase space. A classical phase space contains a real-valued function in 6N dimensions (each particle contributes 3 spatial coordinates and 3 momenta). In this case a "quantum" phase space, on the other hand, involves a complex-valued function on a 3N-dimensional space. The position and momenta are represented by operators that do not commute, and $$\psi$$ lives in the mathematical structure of a Hilbert space. Aside from these differences, however, the rough analogy holds.

Different previously isolated, non-interacting systems occupy different phase spaces. Alternatively we can say that they occupy different lower-dimensional subspaces in the phase space of the joint system. The effective dimensionality of a system's phase space is the number of degrees of freedom present, which—in non-relativistic models—is 6 times the number of a system's free particles. For a macroscopic system this will be a very large dimensionality. When two systems (the environment being one system) start to interact, though, their associated state vectors are no longer constrained to the subspaces. Instead the combined state vector time-evolves a path through the "larger volume", whose dimensionality is the sum of the dimensions of the two subspaces. The extent to which two vectors interfere with each other is a measure of how "close" they are to each other (formally, their overlap or Hilbert space multiplies together) in the phase space. When a system couples to an external environment, the dimensionality of, and hence "volume" available to, the joint state vector increases enormously. Each environmental degree of freedom contributes an extra dimension.

The original system's wave function can be expanded in many different ways as a sum of elements in a quantum superposition. Each expansion corresponds to a projection of the wave vector onto a basis. The basis can be chosen at will. Choosing an expansion where the resulting basis elements interact with the environment in an element-specific way, such elements will—with overwhelming probability—be rapidly separated from each other by their natural unitary time evolution along their own independent paths. After a very short interaction, there is almost no chance of further interference. The process is effectively irreversible. The different elements effectively become "lost" from each other in the expanded phase space created by coupling with the environment. In phase space, this decoupling is monitored through the Wigner quasi-probability distribution. The original elements are said to have decohered. The environment has effectively selected out those expansions or decompositions of the original state vector that decohere (or lose phase coherence) with each other. This is called "environmentally-induced superselection", or einselection. The decohered elements of the system no longer exhibit quantum interference between each other, as in a double-slit experiment. Any elements that decohere from each other via environmental interactions are said to be quantum-entangled with the environment. The converse is not true: not all entangled states are decohered from each other.

Any measuring device or apparatus acts as an environment, since at some stage along the measuring chain, it has to be large enough to be read by humans. It must possess a very large number of hidden degrees of freedom. In effect, the interactions may be considered to be quantum measurements. As a result of an interaction, the wave functions of the system and the measuring device become entangled with each other. Decoherence happens when different portions of the system's wave function become entangled in different ways with the measuring device. For two einselected elements of the entangled system's state to interfere, both the original system and the measuring in both elements device must significantly overlap, in the scalar product sense. If the measuring device has many degrees of freedom, it is very unlikely for this to happen.

As a consequence, the system behaves as a classical statistical ensemble of the different elements rather than as a single coherent quantum superposition of them. From the perspective of each ensemble member's measuring device, the system appears to have irreversibly collapsed onto a state with a precise value for the measured attributes, relative to that element. This provides one explanation of how the Born rule coefficients effectively act as probabilities as per the measurement postulate constituting a solution to the quantum measurement problem.

Dirac notation
Using Dirac notation, let the system initially be in the state

 * $$|\psi\rang = \sum_i |i\rang \lang i |\psi\rang,$$

where the $$|i\rang$$s form an einselected basis (environmentally induced selected eigenbasis ), and let the environment initially be in the state $$|\epsilon\rang$$. The vector basis of the combination of the system and the environment consists of the tensor products of the basis vectors of the two subsystems. Thus, before any interaction between the two subsystems, the joint state can be written as

 * $$|\text{before}\rang = \sum_i |i\rang |\epsilon\rang \lang i|\psi\rang,$$

where $$|i\rang |\epsilon\rang$$ is shorthand for the tensor product $$|i\rang \otimes |\epsilon\rang$$. There are two extremes in the way the system can interact with its environment: either (1) the system loses its distinct identity and merges with the environment (e.g. photons in a cold, dark cavity get converted into molecular excitations within the cavity walls), or (2) the system is not disturbed at all, even though the environment is disturbed (e.g. the idealized non-disturbing measurement). In general, an interaction is a mixture of these two extremes that we examine.

System absorbed by environment
If the environment absorbs the system, each element of the total system's basis interacts with the environment such that

 * $$|i\rang |\epsilon\rang $$ evolves into $$|\epsilon_i\rang,$$

and so

 * $$|\text{before}\rang$$ evolves into $$|\text{after}\rang = \sum_i |\epsilon_i\rang \lang i|\psi\rang.$$

The unitarity of time evolution demands that the total state basis remains orthonormal, i.e. the scalar or inner products of the basis vectors must vanish, since $$\lang i|j\rang = \delta_{ij}$$:

 * $$\lang\epsilon_i|\epsilon_j\rang = \delta_{ij}.$$

This orthonormality of the environment states is the defining characteristic required for einselection.

System not disturbed by environment
In an idealized measurement, the system disturbs the environment, but is itself undisturbed by the environment. In this case, each element of the basis interacts with the environment such that

 * $$|i\rang |\epsilon\rang$$ evolves into the product $$|i, \epsilon_i\rang = |i\rang |\epsilon_i\rang,$$

and so

 * $$|\text{before}\rang$$ evolves into $$|\text{after}\rang = \sum_i |i, \epsilon_i\rang \lang i|\psi\rang.$$

In this case, unitarity demands that

 * $$\lang i, \epsilon_i|j, \epsilon_j\rang = \lang i|j\rang \lang\epsilon_i|\epsilon_j\rang = \delta_{ij} \lang\epsilon_i|\epsilon_j\rang = \delta_{ij} \lang\epsilon_i|\epsilon_i\rang = \delta_{ij},$$

where $$\lang \epsilon_i | \epsilon_i \rang = 1$$ was used. Additionally, decoherence requires, by virtue of the large number of hidden degrees of freedom in the environment, that

 * $$\lang\epsilon_i|\epsilon_j\rang \approx \delta_{ij}.$$

As before, this is the defining characteristic for decoherence to become einselection. The approximation becomes more exact as the number of environmental degrees of freedom affected increases.

Note that if the system basis $$|i\rang$$ were not an einselected basis, then the last condition is trivial, since the disturbed environment is not a function of $$i$$, and we have the trivial disturbed environment basis $$|\epsilon_j\rang = |\epsilon'\rang$$. This would correspond to the system basis being degenerate with respect to the environmentally defined measurement observable. For a complex environmental interaction (which would be expected for a typical macroscale interaction) a non-einselected basis would be hard to define.

Loss of interference and the transition from quantum to classical probabilities
The utility of decoherence lies in its application to the analysis of probabilities, before and after environmental interaction, and in particular to the vanishing of quantum interference terms after decoherence has occurred. If we ask what is the probability of observing the system making a transition from $$\psi$$ to $$\phi$$ before $$\psi$$ has interacted with its environment, then application of the Born probability rule states that the transition probability is the squared modulus of the scalar product of the two states:

 * $$\operatorname{prob}_\text{before}(\psi \to \phi) = \left|\lang\psi|\phi\rang\right|^2 = \left|\sum_i \psi^*_i \phi_i\right|^2 = \sum_i |\psi_i^* \phi_i|^2 + \sum_{ij; i \ne j} \psi^*_i \psi_j \phi^*_j \phi_i ,$$

where $$\psi_i = \lang i|\psi\rang$$, $$\psi_i^* = \lang\psi|i\rang$$, and $$\phi_i = \lang i|\phi\rang$$ etc.

The above expansion of the transition probability has terms that involve $$i \ne j$$; these can be thought of as representing interference between the different basis elements or quantum alternatives. This is a purely quantum effect and represents the non-additivity of the probabilities of quantum alternatives.

To calculate the probability of observing the system making a quantum leap from $$\psi$$ to $$\phi$$ after $$\psi$$ has interacted with its environment, then application of the Born probability rule states that we must sum over all the relevant possible states $$|\epsilon_i\rang$$ of the environment before squaring the modulus:

 * $$\operatorname{prob}_\text{after}(\psi \to \phi) = \sum_j \,\left|\lang\text{after}\right| \phi, \epsilon_j \rang|^2 = \sum_j \,\left|\sum_i \psi_i^* \lang i, \epsilon_i|\phi, \epsilon_j\rang\right|^2 = \sum_j\left|\sum_i \psi_i^* \phi_i \lang\epsilon_i|\epsilon_j\rang \right|^2.$$

The internal summation vanishes when we apply the decoherence/einselection condition $$\lang\epsilon_i|\epsilon_j\rang \approx \delta_{ij}$$, and the formula simplifies to

 * $$\operatorname{prob}_\text{after}(\psi \to \phi) \approx \sum_j |\psi_j^* \phi_j|^2 =

\sum_i |\psi^*_i \phi_i|^2.$$

If we compare this with the formula we derived before the environment introduced decoherence, we can see that the effect of decoherence has been to move the summation sign $$\textstyle\sum_i$$ from inside of the modulus sign to outside. As a result, all the cross- or quantum interference-terms

 * $$\sum_{ij; i \ne j} \psi^*_i \psi_j \phi^*_j \phi_i$$

have vanished from the transition-probability calculation. The decoherence has irreversibly converted quantum behaviour (additive probability amplitudes) to classical behaviour (additive probabilities). However, Ballentine shows that the significant impact of decoherence to reduce interference need not have significance for the transition of quantum systems to classical limits.

In terms of density matrices, the loss of interference effects corresponds to the diagonalization of the "environmentally traced-over" density matrix.

Density-matrix approach
The effect of decoherence on density matrices is essentially the decay or rapid vanishing of the off-diagonal elements of the partial trace of the joint system's density matrix, i.e. the trace, with respect to any environmental basis, of the density matrix of the combined system and its environment. The decoherence irreversibly converts the "averaged" or "environmentally traced-over" density matrix from a pure state to a reduced mixture; it is this that gives the appearance of wave-function collapse. Again, this is called "environmentally induced superselection", or einselection. The advantage of taking the partial trace is that this procedure is indifferent to the environmental basis chosen.

Initially, the density matrix of the combined system can be denoted as

 * $$\rho = |\text{before}\rang \lang\text{before}| = |\psi\rang \lang\psi| \otimes |\epsilon\rang \lang\epsilon|,$$

where $$|\epsilon\rang$$ is the state of the environment. Then if the transition happens before any interaction takes place between the system and the environment, the environment subsystem has no part and can be traced out, leaving the reduced density matrix for the system:

 * $$\rho_\text{sys} = \operatorname{Tr}_\textrm{env}(\rho) = |\psi\rang \lang\psi| \lang\epsilon|\epsilon\rang = |\psi\rang \lang\psi|.$$

Now the transition probability will be given as

 * $$\operatorname{prob}_\text{before}(\psi \to \phi) = \lang\phi| \rho_\text{sys} |\phi\rang = \lang\phi|\psi\rang \lang\psi|\phi\rang = \big|\lang\psi|\phi\rang\big|^2 = \sum_i |\psi_i^* \phi_i|^2 + \sum_{ij; i \ne j} \psi^*_i \psi_j \phi^*_j\phi_i,$$

where $$\psi_i = \lang i|\psi\rang$$, $$\psi_i^* = \lang \psi|i\rang$$, and $$\phi_i = \lang i|\phi\rang$$ etc.

Now the case when transition takes place after the interaction of the system with the environment. The combined density matrix will be

 * $$ \rho = |\text{after}\rang \lang\text{after}| = \sum_{i,j} \psi_i \psi_j^* |i, \epsilon_i\rang \lang j, \epsilon_j| = \sum_{i,j} \psi_i \psi_j^* |i\rang \lang j| \otimes |\epsilon_i\rang \lang\epsilon_j|.$$

To get the reduced density matrix of the system, we trace out the environment and employ the decoherence/einselection condition and see that the off-diagonal terms vanish (a result obtained by Erich Joos and H. D. Zeh in 1985):

 * $$\rho_\text{sys} = \operatorname{Tr}_\text{env}\Big(\sum_{i,j} \psi_i \psi_j^* |i\rang \lang j| \otimes |\epsilon_i\rang \lang\epsilon_j|\Big) = \sum_{i,j} \psi_i \psi_j^* |i\rang \lang j| \lang\epsilon_j|\epsilon_i\rang = \sum_{i,j} \psi_i \psi_j^* |i\rang \lang j| \delta_{ij} = \sum_i |\psi_i|^2 |i\rang \lang i|.$$

Similarly, the final reduced density matrix after the transition will be

 * $$\sum_j |\phi_j|^2 |j\rang \lang j|.$$

The transition probability will then be given as

 * $$\operatorname{prob}_\text{after}(\psi \to \phi) = \sum_{i,j} |\psi_i|^2 |\phi_j|^2 \lang j|i\rang \lang i|j\rang = \sum_i |\psi_i^* \phi_i|^2,$$

which has no contribution from the interference terms

 * $$\sum_{ij; i \ne j} \psi^*_i \psi_j \phi^*_j \phi_i.$$

The density-matrix approach has been combined with the Bohmian approach to yield a reduced-trajectory approach, taking into account the system reduced density matrix and the influence of the environment.

Operator-sum representation
Consider a system S and environment (bath) B, which are closed and can be treated quantum-mechanically. Let $$\mathcal H_S$$ and $$\mathcal H_B$$ be the system's and bath's Hilbert spaces respectively. Then the Hamiltonian for the combined system is

 * $$\hat{H} = \hat H_S \otimes \hat I_B + \hat I_S \otimes \hat H_B + \hat H_I,$$

where $$\hat H_S, \hat H_B$$ are the system and bath Hamiltonians respectively, $$\hat H_I$$ is the interaction Hamiltonian between the system and bath, and $$\hat I_S, \hat I_B$$ are the identity operators on the system and bath Hilbert spaces respectively. The time-evolution of the density operator of this closed system is unitary and, as such, is given by

 * $$\rho_{SB}(t) = \hat U(t) \rho_{SB}(0) \hat U^\dagger(t),$$

where the unitary operator is $$\hat U = e^{-i\hat{H}t/\hbar}$$. If the system and bath are not entangled initially, then we can write $$\rho_{SB} = \rho_S \otimes \rho_B$$. Therefore, the evolution of the system becomes

 * $$\rho_{SB}(t) = \hat U (t)[\rho_S(0) \otimes \rho_B(0)] \hat U^\dagger(t).$$

The system–bath interaction Hamiltonian can be written in a general form as

 * $$\hat H_I = \sum_i \hat S_i \otimes \hat B_i,$$

where $$\hat S_i \otimes \hat B_i$$ is the operator acting on the combined system–bath Hilbert space, and $$\hat S_i, \hat B_i$$ are the operators that act on the system and bath respectively. This coupling of the system and bath is the cause of decoherence in the system alone. To see this, a partial trace is performed over the bath to give a description of the system alone:

 * $$\rho_S(t) = \operatorname{Tr}_B\big[\hat U(t)[\rho_S(0) \otimes \rho_B(0)] \hat U^\dagger(t)\big].$$

$$\rho_S(t)$$ is called the reduced density matrix and gives information about the system only. If the bath is written in terms of its set of orthogonal basis kets, that is, if it has been initially diagonalized, then $$\textstyle\rho_B(0) = \sum_j a_j |j\rangle \langle j|$$. Computing the partial trace with respect to this (computational) basis gives

 * $$\rho_S(t) = \sum_l \hat A_l \rho_S(0) \hat A^\dagger_l,$$

where $$\hat A_l, \hat A^\dagger_l$$ are defined as the Kraus operators and are represented as (the index $$l$$ combines indices $$k$$ and $$j$$):

 * $$\hat A_l = \sqrt{a_j} \langle k| \hat U |j\rangle.$$

This is known as the operator-sum representation (OSR). A condition on the Kraus operators can be obtained by using the fact that $$\operatorname{Tr}[\rho_S(t)] = 1$$; this then gives

 * $$\sum_l \hat A^\dagger_l \hat A_l = \hat I_S.$$

This restriction determines whether decoherence will occur or not in the OSR. In particular, when there is more than one term present in the sum for $$\rho_S(t)$$, then the dynamics of the system will be non-unitary, and hence decoherence will take place.

Semigroup approach
A more general consideration for the existence of decoherence in a quantum system is given by the master equation, which determines how the density matrix of the system alone evolves in time (see also the Belavkin equation  for the evolution under continuous measurement). This uses the Schrödinger picture, where evolution of the state (represented by its density matrix) is considered. The master equation is

 * $$\rho'_S(t) = \frac{-i}{\hbar} \big[\tilde H_S, \rho_S(t)\big] + L_D \big[\rho_S(t)\big],$$

where $$\tilde H_S = H_S + \Delta$$ is the system Hamiltonian $$H_S$$ along with a (possible) unitary contribution $$\Delta$$ from the bath, and $$L_D$$ is the Lindblad decohering term. The Lindblad decohering term is represented as
 * $$L_D\big[\rho_S(t)\big] = \frac{1}{2} \sum_{\alpha, \beta = 1}^M b_{\alpha\beta} \Big(\big[\mathbf F_\alpha, \rho_S(t)\mathbf F^\dagger_\beta\big] + \big[\mathbf F_\alpha \rho_S(t), \mathbf F^\dagger_\beta\big]\Big).$$

The $$\{\mathbf{F}_\alpha\}_{\alpha=1}^M$$ are basis operators for the M-dimensional space of bounded operators that act on the system Hilbert space $$\mathcal H_S$$ and are the error generators. The matrix elements $$b_{\alpha\beta}$$ represent the elements of a positive semi-definite Hermitian matrix; they characterize the decohering processes and, as such, are called the noise parameters. The semigroup approach is particularly nice, because it distinguishes between the unitary and decohering (non-unitary) processes, which is not the case with the OSR. In particular, the non-unitary dynamics are represented by $$L_D$$, whereas the unitary dynamics of the state are represented by the usual Heisenberg commutator. Note that when $$L_D\big[\rho_S(t)\big] = 0$$, the dynamical evolution of the system is unitary. The conditions for the evolution of the system density matrix to be described by the master equation are:
 * 1) the evolution of the system density matrix is determined by a one-parameter semigroup
 * 2) the evolution is "completely positive" (i.e. probabilities are preserved)
 * 3) the system and bath density matrices are initially decoupled

Non-unitary modelling examples
Decoherence can be modelled as a non-unitary process by which a system couples with its environment (although the combined system plus environment evolves in a unitary fashion). Thus the dynamics of the system alone, treated in isolation, are non-unitary and, as such, are represented by irreversible transformations acting on the system's Hilbert space $$\mathcal{H}$$. Since the system's dynamics are represented by irreversible representations, then any information present in the quantum system can be lost to the environment or heat bath. Alternatively, the decay of quantum information caused by the coupling of the system to the environment is referred to as decoherence. Thus decoherence is the process by which information of a quantum system is altered by the system's interaction with its environment (which form a closed system), hence creating an entanglement between the system and heat bath (environment). As such, since the system is entangled with its environment in some unknown way, a description of the system by itself cannot be made without also referring to the environment (i.e. without also describing the state of the environment).

Rotational decoherence
Consider a system of N qubits that is coupled to a bath symmetrically. Suppose this system of N qubits undergoes a rotation around the $$|{\uparrow}\rangle \langle{\uparrow}|, |{\downarrow}\rangle \langle{\downarrow}|$$ $$\big(|0\rangle \langle0|, |1\rangle \langle1|\big)$$ eigenstates of $$\hat{J_z}$$. Then under such a rotation, a random phase $$\phi$$ will be created between the eigenstates $$|0\rangle$$, $$|1\rangle$$ of $$\hat{J_z}$$. Thus these basis qubits $$|0\rangle$$ and $$|1\rangle$$ will transform in the following way:

 * $$|0\rangle \to |0\rangle, \quad |1\rangle \to e^{i\phi} |1\rangle.$$

This transformation is performed by the rotation operator

 * $$R_z(\phi) =

\begin{pmatrix} 1 & 0 \\ 0 & e^{i\phi} \end{pmatrix} .$$

Since any qubit in this space can be expressed in terms of the basis qubits, then all such qubits will be transformed under this rotation. Consider the $$j$$th qubit in a pure state $$\vert\psi_{j}\rangle\langle\psi_{j}\vert$$ where $$|\psi_{j}\rangle = a |0\rangle + b |1\rangle$$. Before application of the rotation this state is:

 * $$ \rho_{j,\text{init}} =

\begin{pmatrix} |a|^2 & ab^{\ast} \\ a^{\ast}b & |b|^2 \end{pmatrix}$$.

This state will decohere, since it is not ‘encoded’ with (dependent upon) the dephasing factor $$e^{i\phi}$$. This can be seen by examining the density matrix averaged over the random phase $$\phi$$:

 * $$\rho_{j} = \mathbb{E}[

R_{z}(\phi) \vert\psi_{j}\rangle \langle\psi_{j}\vert R_{z}^{\dagger}(\phi) ] = \int\limits_{-\infty}^{\infty} R_z(\phi) |\psi_{j}\rangle \langle\psi_{j}|R_z^\dagger(\phi) \;P(\text{d}\phi)$$,

where $$P(\cdot)$$ is a probability measure of the random phase, $$\phi$$. Although not entirely necessary, let us assume for simplicity that this is given by the Gaussian distribution, i.e. $$P(\text{d}\phi) = \frac{1}{\sqrt{2\pi}\sigma}e^{-\frac{1}{2}(\frac{\phi}{\sigma})^{2}}\,\text{d}\phi$$, where $$\sigma$$ represents the spread of the random phase. Then the density matrix computed as above is

 * $$ \rho_{j} =

\begin{pmatrix} |a|^2 & ab^{\ast}\,e^{-\frac{1}{2}\sigma^{2}} \\ a^{\ast}b\,e^{-\frac{1}{2}\sigma^{2}} & |b|^2 \end{pmatrix}$$.

Observe that the off-diagonal elements—the coherence terms—decay as the spread of the random phase, $$\sigma$$, increases over time (which is a realistic expectation). Thus the density matrices for each qubit of the system become indistinguishable over time. This means that no measurement can distinguish between the qubits, thus creating decoherence between the various qubit states. In particular, this dephasing process causes the qubits to collapse to one of the pure states in $$\{ \vert 0\rangle \langle 0\vert, \vert 1\rangle \langle 1\vert \}$$. This is why this type of decoherence process is called collective dephasing, because the mutual phases between all qubits of the N-qubit system are destroyed.

Depolarizing
Depolarizing is a non-unitary transformation on a quantum system which maps pure states to mixed states. This is a non-unitary process because any transformation that reverses this process will map states out of their respective Hilbert space thus not preserving positivity (i.e. the original probabilities are mapped to negative probabilities, which is not allowed). The 2-dimensional case of such a transformation would consist of mapping pure states on the surface of the Bloch sphere to mixed states within the Bloch sphere. This would contract the Bloch sphere by some finite amount and the reverse process would expand the Bloch sphere, which cannot happen.

Dissipation
Dissipation is a decohering process by which the populations of quantum states are changed due to entanglement with a bath. An example of this would be a quantum system that can exchange its energy with a bath through the interaction Hamiltonian. If the system is not in its ground state and the bath is at a temperature lower than that of the system's, then the system will give off energy to the bath, and thus higher-energy eigenstates of the system Hamiltonian will decohere to the ground state after cooling and, as such, will all be non-degenerate. Since the states are no longer degenerate, they are not distinguishable, and thus this process is irreversible (non-unitary).

Timescales
Decoherence represents an extremely fast process for macroscopic objects, since these are interacting with many microscopic objects, with an enormous number of degrees of freedom in their natural environment. The process is needed if we are to understand why we tend not to observe quantum behavior in everyday macroscopic objects and why we do see classical fields emerge from the properties of the interaction between matter and radiation for large amounts of matter. The time taken for off-diagonal components of the density matrix to effectively vanish is called the decoherence time. It is typically extremely short for everyday, macroscale processes. A modern basis-independent definition of the decoherence time relies on the short-time behavior of the fidelity between the initial and the time-dependent state or, equivalently, the decay of the purity.

Mathematical details
Assume for the moment that the system in question consists of a subsystem A being studied and the "environment" $$\epsilon$$, and the total Hilbert space is the tensor product of a Hilbert space $$\mathcal H_A$$ describing A and a Hilbert space $$\mathcal H_\epsilon$$ describing $$\epsilon$$, that is,

 * $$\mathcal H = \mathcal H_A \otimes \mathcal H_\epsilon.$$

This is a reasonably good approximation in the case where A and $$\epsilon$$ are relatively independent (e.g. there is nothing like parts of A mixing with parts of $$\epsilon$$ or conversely). The point is, the interaction with the environment is for all practical purposes unavoidable (e.g. even a single excited atom in a vacuum would emit a photon, which would then go off). Let's say this interaction is described by a unitary transformation U acting upon $$\mathcal H$$. Assume that the initial state of the environment is $$|\text{in}\rangle$$, and the initial state of A is the superposition state

 * $$c_1 |\psi_1\rangle + c_2 |\psi_2\rangle,$$

where $$|\psi_1\rangle$$ and $$|\psi_2\rangle$$ are orthogonal, and there is no entanglement initially. Also, choose an orthonormal basis $$\{ |e_i\rangle \}_i$$ for $$\mathcal H_A$$. (This could be a "continuously indexed basis" or a mixture of continuous and discrete indexes, in which case we would have to use a rigged Hilbert space and be more careful about what we mean by orthonormal, but that's an inessential detail for expository purposes.) Then, we can expand

 * $$U\big(|\psi_1\rangle \otimes |\text{in}\rangle\big)$$

and

 * $$U\big(|\psi_2\rangle \otimes |\text{in}\rangle\big)$$

uniquely as

 * $$\sum_i |e_i\rangle \otimes |f_{1i}\rangle$$

and

 * $$\sum_i |e_i\rangle \otimes |f_{2i}\rangle$$

respectively. One thing to realize is that the environment contains a huge number of degrees of freedom, a good number of them interacting with each other all the time. This makes the following assumption reasonable in a handwaving way, which can be shown to be true in some simple toy models. Assume that there exists a basis for $$\mathcal H_\epsilon$$ such that $$|f_{1i}\rangle$$ and $$|f_{1j}\rangle$$ are all approximately orthogonal to a good degree if i ≠ j and the same thing for $$|f_{2i}\rangle$$ and $$|f_{2j}\rangle$$ and also for $$|f_{1i}\rangle$$ and $$|f_{2j}\rangle$$ for any i and j (the decoherence property).

This often turns out to be true (as a reasonable conjecture) in the position basis because how A interacts with the environment would often depend critically upon the position of the objects in A. Then, if we take the partial trace over the environment, we would find the density state is approximately described by

 * $$\sum_i \big(\langle f_{1i}|f_{1i}\rangle + \langle f_{2i}|f_{2i}\rangle\big) |e_i\rangle \langle e_i|,$$

that is, we have a diagonal mixed state, there is no constructive or destructive interference, and the "probabilities" add up classically. The time it takes for U(t) (the unitary operator as a function of time) to display the decoherence property is called the decoherence time.

Quantitative measurement
The decoherence rate depends on a number of factors, including temperature or uncertainty in position, and many experiments have tried to measure it depending on the external environment.

The process of a quantum superposition gradually obliterated by decoherence was quantitatively measured for the first time by Serge Haroche and his co-workers at the École Normale Supérieure in Paris in 1996. Their approach involved sending individual rubidium atoms, each in a superposition of two states, through a microwave-filled cavity. The two quantum states both cause shifts in the phase of the microwave field, but by different amounts, so that the field itself is also put into a superposition of two states. Due to photon scattering on cavity-mirror imperfection, the cavity field loses phase coherence to the environment. Haroche and his colleagues measured the resulting decoherence via correlations between the states of pairs of atoms sent through the cavity with various time delays between the atoms.

In July 2011, researchers from University of British Columbia and University of California, Santa Barbara showed that applying high magnetic fields to single molecule magnets suppressed two of three known sources of decoherence. They were able to measure the dependence of decoherence on temperature and magnetic field strength.

Applications
Decoherence is a challenge for the practical realization of quantum computers, since such machines are expected to rely heavily on the undisturbed evolution of quantum coherences. They require that the coherence of states be preserved and that decoherence be managed, in order to actually perform quantum computation. The preservation of coherence, and mitigation of decoherence effects, are thus related to the concept of quantum error correction.

In August 2020 scientists reported that ionizing radiation from environmental radioactive materials and cosmic rays may substantially limit the coherence times of qubits if they aren't shielded adequately which may be critical for realizing fault-tolerant superconducting quantum computers in the future.

title: Quantum decoherence


text:
Harmony (toolkit)

The Harmony toolkit is a free software widget toolkit that aimed to be API compatible with the then non-GPL licensed Qt widget toolkit. The QPL license that Qt used was free only if the program was not sold for profit and if its source code was freely available. It was later released under the terms of the GNU Lesser General Public License (LGPL).

In addition to source compatibility with Qt, the Harmony project also aimed to add functionality such as multi-threaded applications and pluggable themes, features that Qt itself later added.

The GNU Project launched the Harmony project, and also the GNOME desktop project, to counter the perceived problem that the free software KDE desktop was gaining popularity but was requiring that people install non GPL licensed software. In July 1997 the GNU Project called for volunteers for a Qt replacement in GNU's Bulletin and listed it as a top priority task on its website.

Development ceased at the end of 2000, when Qt was released under the GPL, removing the perceived need for the Harmony Project to exist. In January 2009 Qt itself was made available under the GNU LGPL, along with the previous license options.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Harmony (toolkit)


text:
User talk:Jptwo

I will reply to comments posted below. -jp2

title: User talk:Jptwo


text:
User talk:Tzuhou

Please say something if you feel like it. There, now I've said it. Tzuhou

Hi
I just wanted to say hi after reading your comments on Talk:Risperidone. Interesting to hear about it from someone who's actually taken it. Marnanel 21:19, 14 Jul 2004 (UTC)

title: User talk:Tzuhou


text:
Jazz scale

A jazz scale is any musical scale used in jazz. Many "jazz scales" are common scales drawn from Western European classical music, including the diatonic, whole-tone, octatonic (or diminished), and the modes of the ascending melodic minor. All of these scales were commonly used by late nineteenth and early twentieth-century composers such as Rimsky-Korsakov, Debussy, Ravel and Stravinsky, often in ways that directly anticipate jazz practice. Some jazz scales, such as the bebop scales, add additional chromatic passing tones to the familiar diatonic scales.

Theory
One important feature of jazz is what theorists call "the principles of chord-scale compatibility": the idea that a sequence of chords will generate a sequence of compatible scales. In classical major-mode harmony, chords typically belong to the same scale. For example, a ii–V–I progression in C major will typically use only the notes of the C diatonic collection. In jazz, a four-chord progression may use four different scales, often as the result of chordal alterations.

For instance, in C major, a jazz musician may alter the V chord, G7 (G–B–D–F), with a flattened fifth, producing the chord G7♭5 (G–B–D♭–F). An improviser might then choose a scale containing these four notes, such as the G whole tone scale, the G octatonic scale, or a mode of either D or A♭ melodic minor ascending. In each case, the scale contains the chord tones G–B–D♭–F and is said to be compatible with it. This notion of "chord scale compatibility" marks a fundamental difference between jazz harmony and traditional classical practice.

An avoid note is a note in a jazz scale that is considered, in jazz theory and practice, too dissonant to be played against the underlying chord, and so is either avoided or chromatically altered. For example, in major-key harmony the 4th, and thus the 11th, is an avoid note and is therefore either treated as a passing tone or is augmented (raised a semitone). Avoid notes are often a minor second (or a minor ninth) above a chord tone or a perfect fourth above the root of the chord.

"[One] can get a good sense of the difference between classical and non-classical harmony from looking at how they deal with dissonances. Classical treats all notes that don't belong to the chord (i.e., the triad) as potential dissonances to be resolved. ... Non-classical harmony just tells you which note in the scale to avoid ['what is sometimes called an avoid-note'] (because it's really dissonant), meaning that all the others are okay."

Modes of the major scale
The number of scales available to improvising musicians continues to expand. As modern techniques and musical constructions appear, jazz players find the ones they can put into compositions or use as material for melodic exploration. Prominent examples are the seven modes of the diatonic major scale and added-note scales.

 * {| class="wikitable" border="1"

!Mode !Name !Scale on C !Associated chord
 * +Modes of the major scale
 * I||Ionian||C–D–E–F–G–A–B–C||Cmaj7 (9, 13)
 * II||Dorian||C–D–E♭–F–G–A–B♭–C||Cm6 or Cm7 (9, 11, 13)
 * III||Phrygian||C–D♭–E♭–F–G–A♭–B♭–C||C7sus (♭9)
 * IV||Lydian||C–D–E–F♯–G–A–B–C||Cmaj7♯11 (9, 13)
 * V||Mixolydian||C–D–E–F–G–A–B♭–C||C7 (9, 13)
 * VI||Aeolian||C–D–E♭–F–G–A♭–B♭–C||Cm7 (9, 11)
 * VII||Locrian||C–D♭–E♭–F–G♭–A♭–B♭–C||Cm7♭5 or C7 (11, ♭13)
 * }
 * V||Mixolydian||C–D–E–F–G–A–B♭–C||C7 (9, 13)
 * VI||Aeolian||C–D–E♭–F–G–A♭–B♭–C||Cm7 (9, 11)
 * VII||Locrian||C–D♭–E♭–F–G♭–A♭–B♭–C||Cm7♭5 or C7 (11, ♭13)
 * }
 * VII||Locrian||C–D♭–E♭–F–G♭–A♭–B♭–C||Cm7♭5 or C7 (11, ♭13)
 * }
 * }

Compare each of the modes to the major scale for clues as to the subtle differences between them. Ionian is based on the 1st degree of the major scale, Dorian on the 2nd, Phrygian on the 3rd, etc.

 * {| class="wikitable" border="1"

!Name !Scale !Associated chord
 * +Modes of the C major scale (White-note scales)
 * C Ionian||C–D–E–F–G–A–B–C||Cmaj7 (9, 13)
 * D Dorian||D–E–F–G–A–B–C–D||Dm6 or Dm7 (9, 11, 13)
 * E Phrygian||E–F–G–A–B–C–D–E||Em7 (♭9)
 * F Lydian||F–G–A–B–C–D–E–F||Fmaj7♯11 (9, 13)
 * G Mixolydian||G–A–B–C–D–E–F–G||G7 (9, 13)
 * A Aeolian||A–B–C–D–E–F–G–A||Am7 (9, 11)
 * B Locrian||B–C–D–E–F–G–A–B||Bm7♭5 or B7 (11, ♭13)
 * }
 * G Mixolydian||G–A–B–C–D–E–F–G||G7 (9, 13)
 * A Aeolian||A–B–C–D–E–F–G–A||Am7 (9, 11)
 * B Locrian||B–C–D–E–F–G–A–B||Bm7♭5 or B7 (11, ♭13)
 * }
 * B Locrian||B–C–D–E–F–G–A–B||Bm7♭5 or B7 (11, ♭13)
 * }
 * }

Bebop scales
Bebop scales add a single chromatic passing tone to the seven-note major scale (Ionian and Mixolydian modes). The added passing tone creates an eight-note scale that fits rhythmically evenly within a measure of 8 eighth notes, thus making it useful in practicing. When an eighth note bebop scale run starts on the beat from a chord tone (i.e. the root, third, fifth or seventh) the other chord notes will also fall on the beat. As a result, all of the nonchord tones will fall on upbeats.

There are two commonly used types of bebop scale:

 * 1) The dominant bebop scale, which adds a chromatic passing tone between the 7th and the root.
 * 2) The major bebop scale, which adds a chromatic passing tone between the 5th and 6th notes.
 * 1) The major bebop scale, which adds a chromatic passing tone between the 5th and 6th notes.

Modes of the melodic minor scale
A great deal of modern jazz harmony arises from the modes of the ascending form of the melodic minor scale, also known as the jazz melodic minor scale. This scale is essentially a diatonic major scale with a lowered third, for example C–D–E♭–F–G–A–B–C. As with any other scale, the modes are derived from playing the scale from different root notes, causing a series of jazz scales to emerge.

 * {| class="wikitable" border="1"

!Mode !Name !Scale on C !Associated chords
 * +Modes of the ascending melodic minor scale on C
 * I||Ascending melodic minor||C–D–E♭–F–G–A–B||Cmmaj7 (9, 11, 13) or Cm6 chords (functions as i minor)
 * II||Dorian ♭2 or Phrygian ♯6||C–D♭–E♭–F–G–A–B♭||C7sus (♭9, ♯9, 13) chord, with ♭2 as a non-chord tone producing a minor ninth
 * III||Lydian augmented||C–D–E–F♯–G♯–A–B||Cmaj7♯5 (9, ♯11) chord (functions as a III+)
 * IV||Acoustic scale, Lydian dominant, Mixolydian ♯4, or Overtone||C–D–E–F♯–G–A–B♭||C7 (9, ♯11, 13) chord (functions as a dominant, secondary, or substitute dominant)
 * V||Aeolian dominant, Mixolydian ♭6, Descending melodic major, or Hindu||C–D–E–F–G–A♭–B♭||C7 (9, ♭13) chord (functions as a dominant with ♭13 as a non-chord tone or the fifth avoided in the chord voicing as they produce a minor ninth)
 * VI||Half-diminished, Locrian ♯2, or Aeolian ♭5||C–D–E♭–F–G♭–A♭–B♭||Cm7♭5 (9, 11, ♭13) (functions as a ii chord in the fifth mode of melodic minor)
 * VII||Altered scale, Super Locrian, or Altered dominant scale||C–D♭–E♭–F♭–G♭–A♭–B♭||C7 (♭9 or ♯9, ♯11, ♭13) chord (functions as a dominant with the fifth of the chord replaced by ♯11 or ♭13, may also be used to harmonize a vii chord in melodic minor)
 * }
 * V||Aeolian dominant, Mixolydian ♭6, Descending melodic major, or Hindu||C–D–E–F–G–A♭–B♭||C7 (9, ♭13) chord (functions as a dominant with ♭13 as a non-chord tone or the fifth avoided in the chord voicing as they produce a minor ninth)
 * VI||Half-diminished, Locrian ♯2, or Aeolian ♭5||C–D–E♭–F–G♭–A♭–B♭||Cm7♭5 (9, 11, ♭13) (functions as a ii chord in the fifth mode of melodic minor)
 * VII||Altered scale, Super Locrian, or Altered dominant scale||C–D♭–E♭–F♭–G♭–A♭–B♭||C7 (♭9 or ♯9, ♯11, ♭13) chord (functions as a dominant with the fifth of the chord replaced by ♯11 or ♭13, may also be used to harmonize a vii chord in melodic minor)
 * }
 * VII||Altered scale, Super Locrian, or Altered dominant scale||C–D♭–E♭–F♭–G♭–A♭–B♭||C7 (♭9 or ♯9, ♯11, ♭13) chord (functions as a dominant with the fifth of the chord replaced by ♯11 or ♭13, may also be used to harmonize a vii chord in melodic minor)
 * }
 * }

Diminished scale
Sometimes called the octatonic scale because it contains eight tones, the diminished scale is composed of a series of alternating half and whole steps. There are two types of diminished scales, one starts with a half step and the other starts with a whole step. The two scales are modes of one another.

Because of the repetition of the interval pattern after only two notes, each note in the scale can be the root in another symmetric diminished scale. For example, the C diminished scale of the half-step-first type, has the same notes as the half-step-first E♭ diminished scale as well as the whole-step-first D♭ diminished scale. All three are composed of the same eight pitches: C–D♭–E♭–E♮–F♯–G–A–B♭–C.

Because of the symmetry of the diminished scale, there are only three distinct diminished scales (shown to the right). The others are all modes of these three.

Whole tone scale
The whole tone scale, consisting exclusively of whole steps, is often used on V7♯5 chords.

Pentatonic scales
Two pentatonic scales common to jazz are the major pentatonic scale and the minor pentatonic scale. They are both modes of one another.

The major pentatonic scale begins with a major scale and omits the fourth and the seventh scale degrees. The minor pentatonic scale uses the same notes as the major pentatonic scale, but begins on the sixth scale degree of the corresponding major scale. In this nomenclature, minor is employed in the sense of relative key, as the diatonic A minor scale is the relative minor of the diatonic C major scale.

Jazz improvisers, particularly bassist and guitarist, use these scales in a number of interesting ways. For example, over B♭maj7♯11, one can use a major pentatonic based on the 2nd scale degree of B♭ (C–D–E–G–A) to imply 9–3–♯11–13–7, respectively. Similarly, over a fully altered F♯7 chord, one can use the same major pentatonic, this time based on the tritone (C–D–E–G–A) to imply ♭5–♭13–♭7–♭9–♯9, respectively.

Blues scale
The term blues scale refers to several different scales with differing numbers of pitches and related characteristics. The six-note blues scale consists of the minor pentatonic scale plus a chromatic passing tone between the 4 and 5. This added note can be spelled as either ♭5 or ♯4. Guitarists often mix the major and minor pentatonics together along with the blues scale.

Another common blues scale has nine notes (shown to the right). Winthrop Sargeant defines this scale as "a definite series of tones within an octave used as the basis of a musical composition," compiled instead from multiple compositions and improvisations (according to Stearns: "a great many jazz records") and is hypothesized as displaying the influence of African music. The E♭ and B♭ are blue notes.

Harmonic minor scale
The harmonic minor scale is also of value to many improvisors, as it provides an alternative color for many common chords and chord progressions. The A harmonic minor scale can be used on the chords of a piece in A minor, especially on the minor ii–V–i chord progression.

One of the most common uses of the harmonic minor scale is its fifth mode, which is a frequently heard sound over dominant chords.

Altered dominant scale
The altered dominant scale, also loosely called the altered scale, is so named because all the scale members that can be altered relative to the basic dominant scale (the Mixolydian mode), without losing the dominant quality, are altered. The scale includes both altered fifths (♭5 and ♯5) and both altered ninths (♭9 and ♯9).

 * Starting on G, it contains the notes: G, A♭, B♭, C♭, D♭, E♭ and F.
 * Starting on C, it contains the notes: C, D♭, E♭, F♭, G♭, A♭ and B♭.

The altered fifths coincide enharmonically with the ♯11 and the ♭13 which would also be considered altered relative to their Mixolydian forms. The tonic, major third (as a diminished fourth), and dominant seventh are retained as essential to the dominant quality.

The scale can also be understood as a mode of the ascending melodic minor scale starting from the 7th scale degree. For a C7 chord, the C♯ melodic minor scale starting from B♯ (C enharmonically) produces the C altered dominant scale enharmonically.

This scale is also called the super-Locrian scale, as it is indeed reminiscent of a Locrian scale with a ♭4, but it is usually regarded as that of major quality. Another name for this scale is the diminished whole-tone scale because the first tetrachord is that of a diminished scale and the second tetrachord is whole-tone.

title: Jazz scale


text:
Sami Al-Arian

Sami Amin Al-Arian (سامي أمين العريان; born January 14, 1958) is a Kuwaiti-born political activist of Palestinian origin who was a computer engineering professor at University of South Florida. During the Clinton administration and Bush administration, he was invited to the White House. He actively campaigned for the Bush presidential campaign in the United States presidential election in 2000.

After a contentious interview with Bill O'Reilly on The O'Reilly Factor following the September 11 attacks, Al-Arian's tenure at University of South Florida came under public scrutiny.

He was indicted in February 2003 on 17 counts under the Patriot Act. A jury acquitted him on 8 counts and deadlocked on the remaining 9 counts. He later struck a plea bargain and admitted to one of the remaining charges in exchange for being released and deported by April 2007. However, as his release date approached, a federal prosecutor in Virginia demanded he testify before a grand jury in a separate case, which he refused to do, claiming it would violate his plea deal. He was held under house arrest in Northern Virginia from 2008 until 2014 when federal prosecutors filed a motion to dismiss charges against him.

Al-Arian's activities and connections became a factor in multiple political campaigns, including the 2004 United States Senate election in Florida and the 2010 United States Senate election in California.

He was deported to Turkey on February 4, 2015.

Kuwait and Egypt
Al-Arian was born on January 14, 1958, in Kuwait. His parents, Amin and Laila Al-Arian, were Palestinian refugees who left after the creation of Israel in 1948. After the 1948 Palestine war, Amin had to leave behind the family soap factory in Jaffa and flee towards the Gaza Strip's refugee camps. Amin's family migrated to Kuwait in 1957 where Sami Al-Arian was born. Under Kuwaiti law, his parents had legal resident status but he was not eligible for citizenship. In 1966, his family left Kuwait and went back to Egypt. He received his primary and secondary education at Cairo, Egypt. He left Egypt in 1975, and returned in 1979 for a visit when he married Nahla Al-Najjar.

United States
Sponsored by his father, Sami went to America for education. In 1975, Al-Arian came to the United States to study engineering at Southern Illinois University. In 1978, he graduated with a major in Electrical Sciences and Systems Engineering. At North Carolina State University, he earned his master's degree in 1980 and doctorate in 1985. He worked with Professor Dharma P. Agrawal on physical failures and fault models of CMOS circuits.

Tenured at University of South Florida
He moved to Temple Terrace after he was hired as an assistant professor to teach computer engineering at University of South Florida (USF) on January 22, 1986. He was granted permanent resident status for United States in March 1989. He was promoted from an assistant professor to an associate professor with tenure. He received many accolades relating to teaching including the Jerome Krivanek Distinguished Teacher Award in 1993 and a salary raise based on merit grades via the Teaching Incentive Program in 1994.

Community involvement and WISE
He was very involved in the local community. He served as an imam for a local mosque and as a charter officer for the local religious school. In 1992, he hosted a local cable-access show — Peace be upon you.

Al-Arian criticized the peace process led by Palestinian Authority president Yasser Arafat and advocated support for the Palestinian uprisings against Israeli occupation during the 1980s and early 1990s. On October 20, 1988, Al-Arian established the Islamic Concern Project, which included a committee devoted to raising charity for Palestine. In 1990–91, his continued involvement in promoting dialogue between the West and Middle East led to the creation of World and Islam Studies Enterprise (WISE), which served as a think tank that promoted public policy initiatives. WISE and University of South Florida formally agreed to cooperate on March 11, 1992. WISE published journals, supported graduate student education, and held seminars between American and Middle Eastern scholars.

Emerson film and investigation
Steve Emerson published a film in November 1994 that accused WISE as a terrorist front organization which Al-Arian vehemently denied. In May 1995, Michael Fechter of the Tampa Tribune expanded on Emerson's film. Sami Al-Arian's daughter, Laila Al-Arian, lambasted Emerson and the Tribune for publishing photographs of their home, school, and family car. In November 1995, federal agents investigating "violations of perjury and immigration laws" searched Sami Al-Arian's home for six hours to seize bank statements dating as far back as 1986, airline passes, telephone bills, AAA travel maps, family videotapes, audiotapes, and computer disks. A three-month independent inquiry was led by prominent Tampa lawyer and former USF President William Reece Smith that involved hundreds of documents and 59 interviews. The investigation reported in May 1996 that there was "no evidence" to support the allegation that Al-Arian or WISE supported terrorism. The report went on to conclude that University of South Florida officials acted appropriately in collaborating with WISE. The 99-page report was lauded by USF President Betty Castor for its "comprehensive, thoughtful, and detailed analysis". In June 1996, Florida universities Chancellor Charles Reed also said their investigation found no links between WISE and terror organizations.

In May 1996, Villanova University canceled a seminar that involved many speakers including Al-Arian after the Anti-Defamation League (ADL) complained about the possibility of riots. The Middle East Studies Association of North America (MESA), the United States's largest association of Middle East scholars, approved a resolution that rebuked ADL for "creating an atmosphere of intimidation that resulted in the cancellation of an academic event". USF placed Al-Arian on paid administrative leave in May 1996 pending the outcome of a federal investigation which had an indefinite time frame. Students complained in August 1997 after a graduation requirement course taught by Al-Arian was cancelled. After consultation with authorities who brought no charges after a three-year federal investigation, USF decided to reinstate him in August 1998.

Citizenship
He applied for U.S. citizenship in January 1994. Although he was informed that he passed all of the requirements to obtain citizenship in September 1994, he was neither granted nor denied citizenship. Federal law requires notification within 120 days after the citizenship examination. In October 1995, he filed suit for a judge to award him citizenship directly. His petition for citizenship was denied in March 1996 for allegedly unlawfully voting in a 1994 Hillsborough County local election.

Mazen Al-Najjar
Sami Al-Arian's brother-in-law Mazen Al-Najjar was jailed for nearly five years, accused of having links to Palestinian terrorists. In May 1997, Al-Najjar was incarcerated in Miami, Florida without charge and was held in jail indefinitely on the basis of secret evidence. Although Judge McHugh found Al-Najjar to be a respected member of a community, McHugh denied bail on the basis of secret evidence in May 1997. In May 2000, U.S. district judge John A. Leonard ordered a rehearing because Al-Najjar's right to due process had been violated when the government did not cede evidence in order for Al-Najjar to defend himself. During the first day of the rehearing in August 2000, the government called Al-Arian to testify. Several legal analysts and Al-Arian were convinced that Al-Arian, not Al-Najjar, was the focus of the Al-Najjar's court case. On the advice of his attorney, Al-Arian cited the 5th Amendment to 99 of 102 questions. Because Al-Najjar was a Palestinian born in Gaza during Egyptian control of the region, Al-Najjar essentially had no citizenship anywhere and the allegations that he was connected to terrorists had ruined attempts to find a country to take him, his wife, and three young daughters. Al-Najjar was released in December 2000 after a judge ruled the government had no evidence to continue holding him. He overstayed his US student visa, and was deported in August 2002.

Political involvement
Inspired by Al-Najjar's predicament, Al-Arian co-founded the Tampa Bay Coalition for Peace and Justice, which focused on the use of secret evidence and other civil rights issues in Antiterrorism and Effective Death Penalty Act of 1996 and Illegal Immigration Reform and Immigrant Responsibility Act of 1996. In 2000, Al-Arian co-founded and led the National Coalition to Protect Political Freedom. Newsweek named him as a "premier civil rights activist" for his efforts to repeal the use of secret evidence in trials.

Al-Arian visited the White House four times from 1997 to 2001.

During the 2000 presidential election, Al-Arian contacted Al Gore's campaign and Bush's campaign to address the use of secret evidence to detain U.S. citizens without charge. Al-Arian met Bush during a campaign stop at the Florida Strawberry Festival to demonstrate against the Clinton administration's use of secret evidence. After presidential debates in which Bush decried the use of secret evidence as a form of racial profiling against Arab-Americans, Al-Arian began campaigning for Bush as the candidate most likely to end discrimination. During the White House briefing that announced Bush as the winner of the election, Al-Arian received a spot in the front row for his voter outreach efforts in Florida. On June 20, 2001, Al-Arian joined 160 Muslim-American activists in a White House briefing with Bush senior adviser Karl Rove. But in a separate White House event on June 28, his son Abdullah – a congressional intern – made national headlines when he was escorted out by Secret Service without explanation. Twenty four Muslim community leaders walked out also to protest Abdullah's ejection. The Secret Service later apologized for the incident citing "confusion by one of its guards". President Bush personally apologized in a letter to Nahla and thanked the family for their charitable contributions to the Muslim communities around the world.

The Tampa Bay Muslim Alliance (TBMA) and Al-Arian had helped the resettlement of 50 families fleeing from the Bosnian War. Al-Arian and other leaders of TBMA condemned the September 11 attacks in the immediate aftermath. Al-Arian encouraged the nation to pursue those responsible but simultaneously discouraged acts of war that might impact innocent people. He discouraged radio talk show hosts from spreading hate-filled rhetoric and called for national unity. Al-Arian led the local Muslim community in organizing a blood drive in solidarity with the victims of September 11.

Al-Arian had opposed the War in Iraq and has spoken at a rally against the war. He has also been critical of neoconservatism and the Zionist movement.

Education
Al-Arian co-founded the Islamic Academy of Florida. After his criminal indictment, the school dissolved itself in 2004, with the new American Youth Academy using the former Islamic Academy buildings and equipment, with most of the students remaining.

Television interview
On September 26, 2001, Al-Arian was invited to appear on The O'Reilly Factor to discuss Arab-American reactions to the 9/11 attacks. O'Reilly never addressed the reactions of Arab-Americans and confronted Al-Arian with a 1988 recording of him shouting "death to Israel".

"O'REILLY: In – in 1988, you did a little speaking engagement in Cleveland, and you were quoted as saying, "Jihad is our path. Victory to Islam. Death to Israel. Revolution. Revolution until victory. Rolling to Jerusalem." Did you say that?

AL-ARIAN: Let me just put it into context. When president Bush talked about crusade, we understand what he meant here. The Muslim world thought he is going to carry a cross and go invade the Muslim world and turn them into Christians. We have to understand the context. When you say "Death to Israel", you mean death to occupation, death to apartheid, death to oppression, death to ... (sentence interrupted)"

O'Reilly ended his interview by calling for the Central Intelligence Agency to shadow Al-Arian. USF spokesman Michael Reich said that "O'Reilly's comments were nothing but speculation." The O'Reilly interview caused Al-Arian to receive death threats from throughout the country.

Academic freedom
In October 2001, USF president Judy Genshaft placed Al-Arian on paid administrative leave and prohibited Al-Arian from entering USF property because she believed Al-Arian's presence would compromise campus security. During winter recess when students and faculty were on leave in December 2001, Genshaft and the USF Board of Trustees declared their intention to fire Al-Arian from teaching at USF because of academic disruption and problems for campus safety. The Faculty Senate President Gregory Paveza condemned the intention to fire as underhanded because the professors did not have their voices heard. The faculty adviser to the Board of Trustees resigned in protest of the firing. The Faculty Senate held an emergency meeting in January 2002 in which they approved by a wide majority a resolution that condemned the firing as an assault on academic freedom. United Faculty of Florida, the faculty union representing USF professors, voted to throw its full support behind Al-Arian and condemned the university for exaggerating security concerns.

CNN did an interview with Al-Arian in January 2002 in which Al-Arian accused the university of allowing those who make death threats to dictate the limits of academic freedom. Florida Governor Jeb Bush entered into the fray when he offered support for Genshaft's decision for Al-Arian's dismissal. An editorial from The New York Times criticized Bush and the university's handling of the case as an affront to freedom of speech. In late January, several student organizations at USF rallied on campus to protest Genshaft's firing of Al-Arian. At the Unitarian Universalist Fellowship in Lakeland in February 2002, Al-Arian discussed the history of the Israeli-Palestinian conflict and answered questions from the community regarding his USF quandary. Roy Weatherford, the President of the USF Faculty Union, lambasted the decision to fire Al-Arian in front of Genshaft in a faculty summit in March 2002. Following the summit, the American Association of University Professors (AAUP) revealed that it was conducting an investigation on Genshaft to determine if she had violated academic freedom. In late April 2002, AAUP investigators reported that Genshaft was wavering on her decision to fire Al-Arian, especially if the university was officially censured. AAUP investigators went on to conclude that Genshaft's decision to place Al-Arian on paid administrative leave rather than suspension reflected her lack of faith in legal advice that green-lighted Al-Arian's firing. USF denied the report and denied that AAUP's decision for censure would factor in Al-Arian's firing.

The largest national teacher's union, American Federation of Teachers, called on Genshaft in July 2002 to protect academic freedom by the reinstatement of Al-Arian. AAUP's investigating committee determined USF's premise for Al-Arian's removal was "insubstantial" and cited "grave issues of academic freedom and due process". Civil libertarians and professors nationwide condemned USF for willingly capitulating to post-9/11 hysteria. Former Central Intelligence Agency (CIA) agent Vincent Cannistraro publicly rebuked allegations against Al-Arian and testified in a civil disposition that Al-Arian had no ties to illegal organizations.

The investments of the Genshaft Family Foundation (GFF) in corporate bonds of the Industrial Development Bank of Israel came under scrutiny in September 2002. Several internet petitions also cited Genshaft's Jewish faith to raise support against Al-Arian. Genshaft denied knowing about the corporate bonds and said her decisions were neither affected by her investments nor her religion in the Al Arian case. John Esposito, a prominent scholar of Middle East, cancelled his USF speech in October 2002 to protest Genshaft's contraventions on academic freedom.

Because Genshaft feared the punitive lawsuits if she fired Al-Arian, Genshaft continued to pursue the Al-Arian's dismissal through an unusual step in which she asked Hillsborough Circuit Court to determine whether firing Al-Arian would violate Al-Arian's First Amendment rights. District Court judge Susan Bucklew dismissed Genshaft's case in December 2002. After Al-Arian filed a grievance contending that Genshaft broke the union contract by disciplining Al-Arian, Genshaft reversed course and affirmed Al-Arian was never disciplined. But a week after a federal indictment on Al-Arian, Genshaft fired him on February 27, 2003, by using the indictment as legal cover to protect the university from any ensuing lawsuit.

Loftus lawsuit
In March 2002, John Loftus compounded on O'Reilly's accusations by citing anonymous sources and filing a lawsuit that claimed Al-Arian used state-regulated organizations to launder money. Al-Arian's defense team derided the lawsuit as a publicity seeking stunt and suggested Loftus needed mental treatment. Loftus's lawsuit was summarily dismissed by the judge for failing to adequately show how Loftus was personally injured by Al-Arian's alleged activities.

Indictment
After one of the Justice Department's longest-running and most controversial terrorism investigations, federal prosecutors filed an indictment on February 21, 2003, which charged Al-Arian with racketeering for Palestine Islamic Jihad (PIJ). Al-Arian was indicted with co-defendants Ghassan Ballut, Hatim Fariz, and Sameeh Hammoudeh. Attorney General John Ashcroft hailed the vastly expanded powers of the Patriot Act as fundamental to the indictment. Arab American groups condemned the indictment as persecution for Al-Arian's advocacy of Palestinian causes. Local community activists, Iraq war protesters, and Muslim-Americans held demonstrations regularly on Al-Arian's affair in the weeks following the indictment. Al-Arian labeled his arrest a consequence of post-9/11 hysteria at a public pronouncement in front of a courthouse rally by his supporters.

In the wake of the indictment of Al-Arian, he became a major issue in the 2004 United States Senate election in Florida. Former USF president Castor, running for Senate, was attacked in the Democratic primary election by opponent Congressman Peter Deutsch and an allied 527 group and in the general election by opponent former HUD Secretary Mel Martinez for not denoucing or firing Al-Arian.

Trial
Al-Arian's five-month, 13-day trial began with frenzied attention from national media outlets. The prosecution's case was built largely on FBI wiretaps and fax transmissions gathered between 1994 and the time of Mr. Al-Arian's arrest in 2003. The surveillance included roughly 20,000 hours of dialogue from 472,000 wiretapped telephone conversations on 18 tapped lines gathered from 1994 to 2003. While such wiretaps taken by the intelligence arm of the FBI are usually kept secret from federal criminal investigators, provisions in the Patriot Act and the Foreign Intelligence Surveillance Act allow their use in certain trials dealing with terrorism. At the end of the prosecution's case, Al-Arian's lawyers chose not to present any witnesses in his defense and rested without offering a defense, hoping to leave the burden of proof squarely on the government's shoulders. The trial concluded in November 2005. After 13 days of deliberations, the jury acquitted Al-Arian in December on 8 of 17 counts and deadlocked on the remaining nine. Two co-defendants were acquitted of all charges and another co-defendant was also acquitted on majority of his charges. The verdict was seen as a major embarrassment to the government's prosecution and to the Patriot Act.

At trial, the prosecution accused Al-Arian of aiding Palestine Islamic Jihad (PIJ), which the Clinton administration issued an executive order declaring the PIJ a "specially designated terrorist" organization in 1995. The executive order barred "making or receiving contributions, funds, goods or services" to benefit the PIJ. Federal prosecutors also presented several transcripts of phone calls, but none involved any discussion of an attack against the U.S. or reflected advance knowledge of attacks in the Middle East.

In April 2005, the faculty union United Faculty of Florida passed resolutions to send a representative to Al-Arian's trial and to express support for Al-Arian's constitutional right to a fair trial with fair treatment of prisoners.

Plea agreement
On February 28, 2006, Al-Arian signed a plea agreement in which he agreed to plead guilty to one count of conspiracy to contribute services to or for the benefit of the PIJ, a Specially Designated Terrorist organization, in violation of 18 U.S.C. § 371. In return, the U.S. Attorney: a) agreed to dismiss the other eight remaining charges in the superseding indictment; b) agreed not to charge Al-Arian with any other crimes known to the government at the time of the execution of the agreement; c) agreed not to enter any recommendation as to the imposition or amount of a fine; d) agreed with Al-Arian that an appropriate sentence would be 46–57 months in prison; and e) covenanted that if no adverse information were received suggesting such a recommendation to be unwarranted, the U.S. would recommend that Al-Arian receive a sentence "at the low end of the applicable guideline range, as calculated by the Court". As part of the deal, Al-Arian agreed to be deported once his prison sentence ended. The plea agreement provided that it was "limited to the Office of the United States Attorney for the Middle District of Florida and the Counterterrorism Section of the Department of Justice, and cannot bind other federal, state, or local prosecuting authorities." It also provided that it "constitutes the entire agreement between the government and [Al-Arian] ... and no other promises, agreements, or representations exist or have been made to [Al-Arian]". The district court judge asked Al-Arian whether he had been promised anything else by anyone to induce his guilty plea, and he said that he had not. The plea agreement was unsealed and accepted by Judge James S. Moody on April 17, 2006. The count carried a maximum sentence of five years imprisonment, a $250,000 fine, and three years of supervised release. Al-Arian remained in custody pending his sentencing and deportation. The deal came after 11 years of Federal Bureau of Investigation investigations, wiretaps and searches, and three and a half years of trial preparation, time Al-Arian spent in jail, most of it in solitary confinement.

Supporters of Al-Arian said the agreement was reached in part to end his family's suffering and to reunite them.

Sentencing
Judge Moody sentenced al-Arian to the maximum 57 months in prison and three years of supervised release on May 1, 2006, and gave him credit for time served. Prosecutors said al-Arian would serve the balance of 19 months, and then be deported. In his ruling, Moody harshly criticized al-Arian. Al-Arian went on a 62-day hunger strike to protest the ruling.

Amnesty International demanded his immediate release and called for an investigation on his treatment in prison. It deemed his pre-trial detention conditions to be "gratuitously punitive" and "inconsistent with international standards for humane treatment". In a 2007 letter to Ashcroft, the human rights organization went on to declare that his "unacceptably harsh and punitive" abuse by prison guards was "based, at least in part, on his political background."

Civil and criminal contempt prosecutions; 2006–present
Al-Arian was subpoenaed three times to testify in terrorism-related investigations before Virginia federal grand juries between 2006 and 2008. Each time, he refused to testify. He challenged the initial subpoena in four different federal courts, each of which held that he was in fact required to testify. He was imprisoned for 13 months for civil contempt for failing to testify in compliance with the first subpoena.

Grand jury subpoenas, refusal to testify, civil contempt, and hunger strikes
In May 2006, the U.S. District Court for the Eastern District of Virginia issued a subpoena to Al-Arian to testify before a federal grand jury in Alexandria, Virginia, in an investigation into the alleged financing of terror by the Herndon, Virginia-based International Institute of Islamic Thought (IIIT). The subpoena was served on Al-Arian in October 2006. He sought to quash it on the assertion that his plea agreement prevented his being forced to testify before the Virginia grand jury. He said the government had agreed that he would not be required to cooperate with it in any manner, though that specific agreement was not reflected in the written plea agreement. In a verbal agreement that he says appears in court transcripts, federal prosecutors agreed he would not have to testify in Virginia. Second, Al-Arian also said he refused to testify because he believed "his life would be in danger if he testified." Third, Al-Arian claimed he has no information that could further the investigation. Fourth, Al-Arian said he would not testify because he felt IIIT was inappropriately charged. When called before the grand jury on October 19, Al-Arian refused to answer questions about IIIT.

A Virginia District Court held that he had no legal basis to refuse to testify. The court held him in civil contempt, and imprisoned him on November 16, 2006, for contempt of court, with the days served for civil contempt not counting towards the days of imprisonment he had remaining on his guilty conspiracy plea. He appealed the Virginia District Court decision to the Fourth Circuit Court of Appeals, which affirmed the lower court's ruling. Thirteen months later, on December 14, 2007, the Virginia District Court lifted its contempt order, starting the clock ticking again on his days-served on his conspiracy guilty plea sentence. A Florida District Court also held that the plea agreement was not ambiguous, and did not prevent the government from issuing a subpoena requiring him to testify before a grand jury. Al-Arian, who is diabetic, began a 60-day hunger strike on January 22, 2007, to "protest continued government harassment." By March 20, 2007, the 6 ft Al-Arian had gone from 202 to 149 lb. Al-Arian appealed the Florida District Court decision to the Eleventh Circuit Court of Appeals, which upheld the lower court on January 25, 2008. It pointed out that the plea agreement did not contain any mention of whether Al-Arian would be compelled to testify in front of a grand jury in the future. It also noted that the agreement said it reflected all promises and agreements between Al-Arian and the government, and that this accorded with Al-Arian's statement, when questioned by the trial court judge, that there were no promises or inducements made to him other than those reflected in the written agreement. Furthermore, the court observed that the plea agreement only spoke to the issue of the government prosecuting Al-Arian for crimes known to the office at the time of the agreement, but did not immunize Al-Arian from future subpoenas. The court therefore held the plea agreement to be clear, unambiguous, and to not grant Al-Arian immunity from the grand jury subpoena. The Justice Department issued its third subpoena later that month.

In March 2008 he began another hunger strike, to protest his subpoena. He ended his hunger strike two months later. A 2011 NPR report claimed some of the people associated with this case were imprisoned in a highly restrictive Communication Management Unit.

Criminal contempt proceedings; house arrest; deportation
On June 26, 2008, he was indicted by a grand jury in the Eastern District of Virginia on two counts of criminal contempt, for unlawfully and willfully refusing court orders that he testify as a grand jury witness on October 16, 2007, and March 20, 2008. On September 2, 2008, he was released from custody and put under house arrest at his daughter Laila's residence in Northern Virginia, where he was monitored electronically while he awaited trial on criminal contempt charges.

At a January 2009 hearing to schedule his trial, his attorneys filed documents saying Al-Arian "did cooperate and answer questions on IIIT" for federal prosecutors. Attorneys alleged Virginia prosecutors are "ultimately not interested in IIIT ... but want to revisit the Tampa trial." In a motion filed on March 4, 2009, prosecutors in Virginia acknowledged that when Al-Arian took the plea deal in early 2006, prosecutors in Tampa believed that it exempted him from testifying in other cases. This affirms sworn declarations submitted to the court by Al-Arian's Florida trial attorneys, Bill Moffitt and Linda Moreno.

On March 9, 2010, Judge Leonie Brinkema postponed the criminal contempt trial, pending a motion by defense attorneys to dismiss the charges in the case. While under federal law, Al-Arian could not be jailed for more than 18 months for civil contempt, the law does not have a time limit for criminal contempt. On June 27, 2014, Assistant U.S. Attorney Gordon D. Kromberg moved to dismiss the indictment, but because the case has dragged on so long they decided to drop the case and begin proceedings to deport Al-Arian.

On February 4, 2015, Al-Arian was deported from the United States to Turkey. He was flown on a commercial flight from Dulles International Airport from Herndon, Virginia to Turkey. In a statement released by his former attorney, Jonathan Turley, Al-Arian said in part, "After 40 years, my time in the U.S. has come to an end." He added, "But despite the long and arduous ordeal and hardships suffered by my family, I leave with no bitterness or resentment in my heart whatsoever. In fact, I'm very grateful for the opportunities and experiences afforded to me and my family in this country, and for the friendships we've cultivated over the decades. These are lifelong connections that could never be affected by distance."

In 2017, Al-Arian founded the Center for Islam and Global Affairs (CIGA) at Istanbul Sabahattin Zaim University (IZU) in Istanbul, Turkey, which he directs.

In 2024, the New York Police Department and Mayor Eric Adams stated that Al-Arian posted on Twitter a photo of his wife at the 2024 Columbia University pro-Palestinian campus occupation. Adams cited the posting as evidence of non Columbia-affiliated individuals training and providing tactics to students to escalate their protests.

Personal life
He is married to Nahla Al-Najjar, and they have five children. Nahla was born in 1960. His son Abdullah Al-Arian was an intern for U.S. Representative David E. Bonior in 2001. Al-Arian's eldest daughter, Laila Al-Arian, is a producer for Al Jazeera English in Washington, D.C., and a freelance journalist and contributor to the Huffington Post and The Nation.

Film
USA vs. Al-Arian is a 2007 documentary film by Norwegian director Line Halvorsen about Al-Arian and his family during and after his trial from his family's point of view, and a commentary on the U.S. justice system under the Patriot Act. The documentary was hosted by two MPs and screened in the Norwegian parliament.

title: Sami Al-Arian


text:
User talk:JuniorJetKaptain

Gone. JuniorJetKaptain 18:52, 10 December 2006 (UTC)

title: User talk:JuniorJetKaptain