Quantum process tomography of single-photon quantum channels with controllable decoherence

Shaham, Assaf; Eisenberg, Henryk

doi:10.1088/0031-8949/2012/t147/014029

Cited by 8 publications

(9 citation statements)

References 16 publications

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“…Or perhaps not. Empirical methods have been developed to characterize such systems more systematically; however, so far as we know, they have only been used to validate larger systems 11 , and not to probe the exact nature of polarizer imperfections. The polarizer models here also suggest that study of the black body property of polarizers, such as red hot calcite prisms, might yield interesting information.…”

Section: Immediate Questionsmentioning

confidence: 99%

Example of lumped parameter modeling of a quantum optics circuit

Werbos¹

2014

Quantum Information and Computation XII

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Is it possible for a simple lumped parameter model of a circuit to yield correct quantum mechanical predictions of its behavior, when there is quantum entanglement between components of that circuit? This paper shows that it is possible in a simple but important example -the circuit of the original Bell's Theorem experiments, for ideal polarizers. Correct predictions emerge from two alternative simple models, based on classical Markov Random Fields (MRF) across spacetime, which are local and realistic and symmetric with respect to time. Exact agreement with quantum mechanics does not violate Bell's Theorem itself, because the interplay between initial and final outcomes in these calculations does not meet the classical definition of time-forwards causality. Both models raise interesting questions for future research. The final section discusses several possible directions for following up on these results, both in lumped system modeling and in more formal and general approaches. It describes how a new all-angles triphoton experiment, not yet performed, would decisively tell us which is true, either the time-symmetric MRF models or the time-forwards collapse model assumed in the usual measurement formalism of Copenhagen quantum mechanics. A new appendix calculates what the Copenhagen measurement formalism predicts for the triphoton experiment, and provides a continuous time formulation of the usual collapse of the wave function without metaphysical observers.

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Section: Immediate Questionsmentioning

confidence: 99%

Example of lumped parameter modeling of a quantum optics circuit

Werbos¹

2014

Quantum Information and Computation XII

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“…Two different unital channels were implemented. The first is the two-field channel 21 22 , (see Fig. 1b ).…”

Section: Resultsmentioning

confidence: 99%

Entanglement dynamics in the presence of controlled unital noise

Shaham

Halevy

Dovrat

et al. 2015

Sci Rep

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Quantum entanglement is notorious for being a very fragile resource. Significant efforts have been put into the study of entanglement degradation in the presence of a realistic noisy environment. Here, we present a theoretical and an experimental study of the decoherence properties of entangled pairs of qubits. The entanglement dynamics of maximally entangled qubit pairs is shown to be related in a simple way to the noise representation in the Bloch sphere picture. We derive the entanglement level in the case when both qubits of a Bell state are transmitted through any arbitrary unital Pauli channel, and compare it to the case when the channel is applied only to one of the qubits. The dynamics of both cases was verified experimentally using an all-optical setup. We further investigated the evolution of partially entangled initial states. Different dynamics was observed for initial mixed and pure states of the same entanglement level.

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“…In Fig. 3, we draw the eigenvalues of the two process matrixes, which can be served as a measure for the decoherence [19]. Because the eigenvalues fluctuate in a small amount, it indicates that the quantum channel barely costs decoherence to the qubit.…”

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confidence: 99%