Phase diffusion in quantum dissipative systems

Banerjee, Subhashish; Srikanth, R.

doi:10.1103/physreva.76.062109

Cited by 23 publications

(34 citation statements)

References 74 publications

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“…The qubit state ρ ξ of Eq. (27) has eigenvalues λ ± = (1 ± r )/2 and normalized eigenvectors |λ ± , the two projectors on these eigenvectors having the Bloch representation |λ ± λ ± | = (1 ± r σ / r )/2. The state of Eq.…”

Section: A Quantum Fisher Information For the Qubitmentioning

confidence: 99%

“…Such a noise process describes the interaction of the qubit with a squeezed thermal bath. Squeezing of a thermal bath is obtained by a nonlinear operation capable of introducing correlations between the modes or thermal photons of the bath, with possibilities to counteract the detrimental decohering effect of temperature [24,25,27]. The SGAD quantum noise is characterized in Eq.…”

Section: Nonunital Noisesmentioning

confidence: 99%

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Optimized probing states for qubit phase estimation with general quantum noise

Chapeau‐Blondeau

2015

Phys. Rev. A

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We exploit the theory of quantum estimation to investigate quantum state estimation in the presence of noise. The quantum Fisher information is used to assess the estimation performance. For the qubit in Bloch representation, general expressions are derived for the quantum score and then for the quantum Fisher information. From this latter expression, it is proved that the Fisher information always increases with the purity of the measured qubit state. An arbitrary quantum noise affecting the qubit is taken into account for its impact on the Fisher information. The task is then specified to estimating the phase of a qubit in a rotation around an arbitrary axis, equivalent to estimating the phase of an arbitrary single-qubit quantum gate. The analysis enables determination of the optimal probing states best resistant to the noise, and proves that they always are pure states but need to be specifically matched to the noise. This optimization is worked out for several noise models important to the qubit. An adaptive scheme and a Bayesian approach are presented to handle phase-dependent solutions.

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Section: A Quantum Fisher Information For the Qubitmentioning

confidence: 99%

Section: Nonunital Noisesmentioning

confidence: 99%

Optimized probing states for qubit phase estimation with general quantum noise

Chapeau‐Blondeau

2015

Phys. Rev. A

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“…The squeezed generalized amplitude damping (SGAD) [45,46] is a very general dissipative channel of the Lindblad class and incorporates the well known amplitude damping and generalized amplitude damping channels as limiting cases. The role of the squeezed thermal bath in the present context is very pertinent as squeezing is connected to parametric amplification which is known to play an important role in the context of particle creation [1,2,9] and at the same time plays a constructive role in preserving quantum coherence in the presence of decoherence [45,47,48].…”

Section: Jhep02(2017)082mentioning

confidence: 99%

Characterization of Unruh channel in the context of open quantum systems

Banerjee

Alok

Omkar

et al. 2017

J. High Energ. Phys.

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Abstract:In this work, we study an important facet of field theories in curved spacetime, viz. the Unruh effect, by making use of ideas of statistical mechanics and quantum foundations. Aspects of decoherence and dissipation, natural artifacts of open quantum systems, along with foundational issues such as the trade-off between coherence and mixing as well as various aspects of quantum correlations are investigated in detail for the Unruh effect. We show how the Unruh effect can be quantified mathematically by the Choi matrix approach. We study how environmentally induced decoherence modifies the effect of the Unruh channel. The differing effects of a dissipative or non-dissipative environment are noted. Further, useful parameters characterizing channel performance such as gate and channel fidelity are applied here to the Unruh channel, both with and without external influences. Squeezing, which is known to play an important role in the context of particle creation, is shown to be a useful resource in a number of scenarios.

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“…Figure 1 also demonstrates that the performance in detection improves at larger squeezing magnitude r . This is a mark of the ability of squeezing of the thermal bath to counteract the detrimental effect of temperature, as also noted in [19], [20], and [23] with other performance measures. A complementary picture is given by Fig.…”

Section: Squeezed Generalized Amplitude Damping Noisementioning

confidence: 98%

Optimization of Quantum States for Signaling Across an Arbitrary Qubit Noise Channel With Minimum-Error Detection

Chapeau‐Blondeau

2015

IEEE Trans. Inform. Theory

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For discrimination between two signaling states of a qubit, the optimal detector minimizing the probability of error is applied to the situation where detection has to be performed from a noisy qubit affected by an arbitrary quantum noise separately characterized. With no noise, any pair of orthogonal pure quantum states is optimal for signaling as it enables error-free detection. In the presence of noise, detection errors are in general inevitable, and the pairs of signaling states best resistant to such noise are investigated. With an arbitrary quantum noise, modeled as a channel affecting the qubit, and when minimum-error detection is performed from the output, a characterization of the optimal input signaling pairs and of their best detection performance is obtained through a simple maximization of a quadratic scalar criterion in three constrained real variables. This general characterization enables to establish that such optimal signaling pairs are always made of two orthogonal pure quantum states, but that they must be specifically selected to match the noise properties and prior probabilities. The maximization is explicitly solved for several generic quantum noise processes relevant to the qubit, such as the squeezed generalized amplitude damping noise which describes interaction with a thermal bath representing a decohering environment and which includes as special cases both the generalized and the regular amplitude damping noise processes, and such as general Pauli noise processes which include for instance the bit-flip noise and the depolarizing noise. Also, examined is the situation of one imposed (pure or mixed) signaling state, for which the other associated signaling state optimal for noisy detection is determined as a pure state, yet not necessarily orthogonal.Index Terms-Quantum state discrimination, quantum detection, quantum noise, noisy qubit, decoherence.

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Phase diffusion in quantum dissipative systems

Cited by 23 publications

References 74 publications

Optimized probing states for qubit phase estimation with general quantum noise

Optimized probing states for qubit phase estimation with general quantum noise

Characterization of Unruh channel in the context of open quantum systems

Optimization of Quantum States for Signaling Across an Arbitrary Qubit Noise Channel With Minimum-Error Detection

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