Coherent-state spin qubits in the presence of spin-orbit coupling

We provide an in-depth investigation of parameter estimation in Nested Mach-Zehnder interferometers (NMZIs) using two information measures: the Fisher information and the Shannon mutual information. Protocols for counterfactual communition (CFC) have, so far, been based on two different definitions of counterfactuality. In particular, some schemes are been based on NMZI devices, and have recently been subject to criticism. We provide a methodology for evaluating the counterfactuality of these protocols, based on an information theoretical framework. More specifically, we make the assumption that any realistic quantum channel in MZI structures will have some weak uncontrolled interaction. We then use the Fisher information of this interaction to measure counterfactual violations. The measure is used to evaluate the suggested counterfactual communication protocol of Salih et al. [1]. The protocol of Arvidsson-Shukur and Barnes [2], based on a different definition, is evaluated with a probability measure. Our results show that the definition of Arvidsson-Shukur and Barnes is satisfied by their scheme, whilst that of Salih et al. is only satisfied by perfect quantum channels. For realistic devices the latter protocol does not achieve its objective.

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“…The solution is calculated by a GPU-boosted version of the Staggered Leapfrog algorithm as in Refs. [41,42]. Fig.…”

Section: Simulation Of Quantum Evolutionmentioning

confidence: 98%

Evaluation of counterfactuality in counterfactual communication protocols

2017

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“…The solution is obtained using an accelerated Staggered Leapfrog algorithm as in Ref. [40]. The wavefunction evolution is outlined in Fig.…”

Section: Numerical Demonstrationmentioning

confidence: 99%

Quantum counterfactual communication without a weak trace

Arvidsson-Shukur

Barnes

2016

Phys. Rev. A

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The classical theories of communication rely on the assumption that there has to be a flow of particles from Bob to Alice in order for him to send a message to her. We develop a quantum protocol that allows Alice to perceive Bob's message "counterfactually". That is, without Alice receiving any particles that have interacted with Bob. By utilising a setup built on results from interactionfree measurements, we outline a communication protocol whereby the information travels in the opposite direction of the emitted particles. In comparison to previous attempts on such protocols, this one is such that a weak measurement at the message source would not leave a weak trace that could be detected by Alice's receiver. Whilst some interaction-free schemes require a large number of carefully aligned beam-splitters, our protocol is realisable with two or more beam-splitters. We demonstrate this protocol by numerically solving the time-dependent Schrödinger Equation (TDSE) for a Hamiltonian that implements this quantum counterfactual phenomenon.

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“…The electron qubit may be implemented in several ways 13 : as a charge qubit [14][15][16][17][18][19] , a spin qubit 20,21 or encoded in electronic Schrödinger cat states 22,23 . The solidstate qubit based on electron spin in electrostatic quantum dots is the easiest to implement and is one of a few promising candidates for quantum computing 24 .…”

Section: Introductionmentioning

confidence: 99%

All-electric single-electron spin-to-charge conversion

et al. 2018

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We examine spin-dependent displacement of a single electron, resulting in separation and relocation of the electron wavefunction components, and thus charge parts, corresponding to opposite spins. This separation is induced by a pulse of an electric field which generates varying Rashba type spin-orbit coupling. This mechanism is next implemented in a nanodevice based on a gated quantum dot defined within a quantum nanowire. The electric field pulse is generated by ultrafast changes of voltages, of the order of several hundred mV, applied to nearby gates. The device is modeled realistically with appropriate material parameters and voltages applied to the gates, yielding an accurate confinement potential and Rashba coupling. At the end, we propose a spin-to-charge conversion device, which with an additional charge detector will allow for electron spin state measurement.

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Coherent-state spin qubits in the presence of spin-orbit coupling

Cited by 10 publications

References 35 publications

Evaluation of counterfactuality in counterfactual communication protocols

Evaluation of counterfactuality in counterfactual communication protocols

Quantum counterfactual communication without a weak trace

All-electric single-electron spin-to-charge conversion

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