Quantum state discrimination and enhancement by noise

Chapeau‐Blondeau, François

doi:10.1016/j.physleta.2014.05.025

Cited by 10 publications

(4 citation statements)

References 63 publications

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“…(37) a decrease of the purity r(ξ ) of the measured noisy state ρ ξ , and hence a decrease of the quantum Fisher information F q (ξ ). Such types of unexpected counterintuitive behaviors might be compared to stochastic resonance or useful-noise effects occurring in classical estimation [15][16][17] or quantum information processing [18][19][20].…”

Section: B Noise On the Qubitmentioning

confidence: 99%

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: B Noise On the Qubitmentioning

confidence: 99%

Optimized probing states for qubit phase estimation with general quantum noise

Chapeau‐Blondeau

2015

Phys. Rev. A

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“…Various forms of stochastic resonance have recently been reported in informational processes involving the qubit in the presence of noise. Forms of stochastic resonance have been investigated for information communication over qubit channels [21][22][23][24]. For quantum sensors and metrology, stochastic resonance has recently been extended to situations of quantum state detection [25] or quantum state estimation [26,27] from noisy qubits.…”

Section: Introductionmentioning

confidence: 99%

Stochastic Resonance with Unital Quantum Noise

2019

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The fundamental quantum information processing task of estimating the phase of a qubit is considered. Following quantum measurement, the estimation efficiency is evaluated by the classical Fisher information which determines the best performance limiting any estimator and achievable by the maximum likelihood estimator. The estimation process is analyzed in the presence of decoherence represented by essential quantum noises that can affect the qubit and belonging to the broad class of unital quantum noises. Such a class especially contains the bit-flip, the phase-flip, the depolarizing noises, or the whole family of Pauli noises. As the level of noise is increased, we report the possibility of non-standard behaviors where the estimation efficiency does not necessarily deteriorate uniformly, but can experience non-monotonic variations. Regimes are found where higher noise levels prove more favorable to estimation. Such behaviors are related to stochastic resonance effects in signal estimation, shown here feasible for the first time with unital quantum noises. The results provide enhanced appreciation of quantum noise or decoherence, manifesting that it is not always detrimental for quantum information processing.

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“…In the classical (non‐quantum) context, such effects of noise‐enhanced performance have been reported in numerous processes, especially for signal estimation [4, 5], and related to the phenomenon of stochastic resonance [6]. In the context of quantum information, several processes with noise‐enhanced performance have been reported [7–9]. Yet it is the first time to our knowledge that noise‐enhanced performance is shown feasible for quantum state estimation as considered here.…”

Section: Introductionmentioning

confidence: 99%

Qubit state estimation and enhancement by quantum thermal noise

Chapeau‐Blondeau

2015

Electron. lett.

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From a qubit in a noisy state affected by an uncontrolled decohering environment represented by a thermal bath at temperature T, estimation of the norm of its Bloch vector is considered, equivalent to estimation of its purity or of its linear entropy. The performance in estimation is assessed by the quantum Fisher information. When the qubit can be prepared with an optimal orientation precisely matched to the thermal noise, the estimation performance always degrades with an increasing temperature of the bath. On the contrary, for a non-optimal orientation of the qubit, the possibility of an enhancement of the estimation performance with an increasing temperature of the bath is demonstrated. Such behaviour shows that increased decoherence is not necessarily associated with poorer informational performance, and can be compared with stochastic resonance or useful noise effects previously reported in classical (non-quantum) estimation.

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Quantum state discrimination and enhancement by noise

Cited by 10 publications

References 63 publications

Optimized probing states for qubit phase estimation with general quantum noise

Optimized probing states for qubit phase estimation with general quantum noise

Stochastic Resonance with Unital Quantum Noise

Qubit state estimation and enhancement by quantum thermal noise

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