Optimal coherent control of dissipative<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>N</mml:mi></mml:math>-level systems

Jirari, H.; Pötz, W.

doi:10.1103/physreva.72.013409

Cited by 75 publications

(79 citation statements)

References 23 publications

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“…One of the most difficult problems of QC is that unavoidable coupling of the quantum information processor (QIP) to the environment results in a loss of coherence. In recent years, significant attention was devoted to various methods of dynamic suppression of environmentally-induced decoherence in open quantum systems, including applications of pre-designed external fields [4,5,6,7,8] and optimal control techniques [9,10,11,12,13,14,15]. In a separate line of research, several works [16,17,18,19,20,21] considered the generation of optimally controlled unitary quantum gates in ideal situations where coupling to the environment can be neglected during the gate operation.…”

Section: Introductionmentioning

confidence: 99%

Fidelity of optimally controlled quantum gates with randomly coupled multiparticle environments

Grace

Brif

Rabitz

et al. 2007

Journal of Modern Optics

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This work studies the feasibility of optimal control of high-fidelity quantum gates in a model of interacting two-level particles. One particle (the qubit) serves as the quantum information processor, whose evolution is controlled by a time-dependent external field. The other particles are not directly controlled and serve as an effective environment, coupling to which is the source of decoherence. The control objective is to generate target one-qubit gates in the presence of strong environmentally-induced decoherence and under physically motivated restrictions on the control field. It is found that interactions among the environmental particles have a negligible effect on the gate fidelity and require no additional adjustment of the control field. Another interesting result is that optimally controlled quantum gates are remarkably robust to random variations in qubit-environment and inter-environment coupling strengths. These findings demonstrate the utility of optimal control for management of quantum-information systems in a very precise and specific manner, especially when the dynamics complexity is exacerbated by inherently uncertain environmental coupling.

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Section: Introductionmentioning

confidence: 99%

Fidelity of optimally controlled quantum gates with randomly coupled multiparticle environments

Grace

Brif

Rabitz

et al. 2007

Journal of Modern Optics

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“…In addition to applications to the problem of dynamical suppression of decoherence [22,23,24,25,26,27], optimal control theory (OCT) [31,32] was also successfully used to design unitary quantum gates in closed systems [33,34,35,36,37]. The optimal control of quantum gates in the presence of decoherence still remains to be fully explored.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, it is very important to decrease the errors caused by decoherence. This problem has inspired significant interest in various methods of decoherence management, including the use of decoherence-free subspaces and noiseless subsystems [8,9,10,11,12], quantum dynamical decoupling [13,14,15,16,17,18,19,20], schemes based on stochastic control [21], optimal control techniques [22,23,24,25,26,27], and multilevel encoding of logical states [28].…”

Section: Introductionmentioning

confidence: 99%

Optimal control of quantum gates and suppression of decoherence in a system of interacting two-level particles

Grace

Brif

Rabitz

et al. 2007

J. Phys. B: At. Mol. Opt. Phys.

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Abstract. Methods of optimal control are applied to a model system of interacting two-level particles (e.g., spin-half atomic nuclei or electrons or two-level atoms) to produce high-fidelity quantum gates while simultaneously negating the detrimental effect of decoherence. One set of particles functions as the quantum information processor, whose evolution is controlled by a time-dependent external field. The other particles are not directly controlled and serve as an effective environment, coupling to which is the source of decoherence. The control objective is to generate target one-and two-qubit unitary gates in the presence of strong environmentallyinduced decoherence and under physically motivated restrictions on the control field. The quantum-gate fidelity, expressed in terms of a novel state-independent distance measure, is maximized with respect to the control field using combined genetic and gradient algorithms. The resulting high-fidelity gates demonstrate the feasibility of precisely guiding the quantum evolution via optimal control, even when the system complexity is exacerbated by environmental coupling. It is found that the gate duration has an important effect on the control mechanism and resulting fidelity. An analysis of the sensitivity of the gate performance to random variations in the system parameters reveals a significant degree of robustness attained by the optimal control solutions.

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“…The field couples to the qubit by the same operator σ x 1 as the bath, i.e., "perpendicular" to the static Hamiltonian (15). Thus, it commutes with the qubit-bath coupling but not with the static Hamiltonian.…”

Section: Coherent Destruction Of Tunnelingmentioning

confidence: 99%

“…The unavoidable coupling to external degrees of freedom and the thereby caused decoherence still presents a main obstacle for the realization of a quantum computer. Several proposals to overcome the ensuing decoherence have been put forward, such as the use of decoherence free subspaces [8][9][10][11][12], coherence-preserving qubits [13], quantum Zeno subspaces [14], optimized pulse sequences [15,16], dynamical decoupling [17][18][19][20][21], and coherent destruction of tunneling [22,23]. Theoretical studies of decoherence of two-level systems have been extended to gate operations in the presence of an environment in [24][25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%