Relativistic quantum information and time machines

Ralph, T. C.; Downes, T.

doi:10.1080/00107514.2011.640146

Cited by 37 publications

(36 citation statements)

References 108 publications

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“…where the right-hand side shows the equivalent of the conformal time expression in Minkowski time, with + (−) for the future (past) coordinates, we can observe that a physical detector that follows the conformal time of equation (2) (with 0 ϵ = ) corresponds to a detector with time dependent energy-level spacings ( H at o ± ). This observation was confirmed in [7] and [8] via the explicit calculation of the excitation rates and correlation properties of Unruh-DeWitt detectors, coupled to the Minkowski vacuum and given time dependent resonant frequencies according to equation (3). This demonstrated that inertial, energy scaled detectors of this type could indeed couple to the Rindler modes as expected and hence observe the intrinsic entanglement in the quantum vacuum.…”

Section: Rindler and Light Cone Coordinatessupporting

confidence: 61%

“…We have shown that by employing energy-scaled homodyne detection it is possible for two observers, separated by non-trivial distances, to measure the correlations of entangled space-time vacuum modes with sufficient quality so as to be able to implement a QKD protocol. The energy levels of the detectors must change with lab time according to Hamiltonians obeying equation (3). The local oscillators should also follow this scaling.…”

Section: Discussionmentioning

confidence: 99%

“…To be consistent with the coordinates of equation (2), and hence to couple to the Rindler modes, we need the energy levels of all the absorbers in our macroscopic detectors to scale according to the Schrödinger equation, equation (3). In addition we need the centre frequency of the local oscillator to also scale in this way (see the appendix for more details).…”

Section: Homodyne Detection Of Rindler Entanglementmentioning

confidence: 99%

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Quantum key distribution without sending a quantum signal

Ralph

Walk

2015

New J. Phys.

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Quantum Key Distribution is a quantum communication technique in which random numbers are encoded on quantum systems, usually photons, and sent from one party, Alice, to another, Bob. Using the data sent via the quantum signals, supplemented by classical communication, it is possible for Alice and Bob to share an unconditionally secure secret key. This is not possible if only classical signals are sent. While this last statement is a long standing result from quantum information theory it turns out only to be true in a non-relativistic setting. If relativistic quantum field theory is considered we show it is possible to distribute an unconditionally secure secret key without sending a quantum signal, instead harnessing the intrinsic entanglement between different regions of space-time. The protocol is practical in free space given horizon technology and might be testable in principle in the near term using microwave technology.

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Section: Rindler and Light Cone Coordinatessupporting

confidence: 61%

Section: Discussionmentioning

confidence: 99%

Section: Homodyne Detection Of Rindler Entanglementmentioning

confidence: 99%

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Quantum key distribution without sending a quantum signal

Ralph

Walk

2015

New J. Phys.

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“…The novel field of relativistic quantum information aims at understanding how relativity affects quantum information tasks [11,12]. Most of hitherto research has focused on modeling and employing localized systems for quantum information processing [13][14][15], while only recently some attention has been drawn towards understanding the influence of gravity on quantum protocols.…”

Section: Introductionmentioning

confidence: 99%

Spacetime effects on satellite-based quantum communications

et al. 2014

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We investigate the consequences of space-time being curved on space-based quantum communication protocols. We analyze tasks that require either the exchange of single photons in a certain entanglement distribution protocol or beams of light in a continuous-variable quantum key distribution scheme. We find that gravity affects the propagation of photons, therefore adding additional noise to the channel for the transmission of information. The effects could be measured with current technology.

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“…A certain type of quantum gates without definite temporal order (acausal gates) has been modeled based on postselected quantum teleportation [6,7]. These gates are referred to as closed timelike curves via quantum postselection (pCTCs, or also known as BSS-CTCs) and their properties have been recently intensively investigated [8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Parallelizable adiabatic gate teleportation

et al. 2015

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To investigate how a temporally ordered gate sequence can be parallelized in adiabatic implementations of quantum computation, we modify adiabatic gate teleportation, a model of quantum computation proposed by D. Bacon and S. T. Flammia, Phys. Rev. Lett. 103, 120504 (2009), to a form deterministically simulating parallelized gate teleportation, which is achievable only by postselection. We introduce a twisted Heisenberg-type interaction Hamiltonian, a Heisenberg-type spin interaction where the coordinates of the second qubit are twisted according to a unitary gate. We develop parallelizable adiabatic gate teleportation (PAGT) where a sequence of unitary gates is performed in a single step of the adiabatic process. In PAGT, numeric calculations suggest the necessary time for the adiabatic evolution implementing a sequence of L unitary gates increases at most as O(L 5 ). However, we show that it has the interesting property that it can map the temporal order of gates to the spatial order of interactions specified by the final Hamiltonian. Using this property, we present a controlled-PAGT scheme to manipulate the order of gates by a control-qubit. In the controlled-PAGT scheme, two differently ordered sequential unitary gates F G and GF are coherently performed depending on the state of a control-qubit by simultaneously applying the twisted Heisenberg-type interaction Hamiltonians implementing unitary gates F and G. We investigate why the twisted Heisenberg-type interaction Hamiltonian allows PAGT. We show that the twisted Heisenberg-type interaction Hamiltonian has an ability to perform a transposed unitary gate by just modifying the space ordering of the final Hamiltonian implementing a unitary gate in adiabatic gate teleportation. The dynamics generated by the time-reversed Hamiltonian represented by the transposed unitary gate enables deterministic simulation of a postselected event of parallelized gate teleportation in adiabatic implementation.

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Relativistic quantum information and time machines

Cited by 37 publications

References 108 publications

Quantum key distribution without sending a quantum signal

Quantum key distribution without sending a quantum signal

Spacetime effects on satellite-based quantum communications

Parallelizable adiabatic gate teleportation

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