Experimental quantum communication enhancement by superposing trajectories

Rubino, Giulia; Rozema, Lee A.; Ebler, Daniel; Kristjánsson, Hlér; Salek, Sina; Guérin, Philippe; Abbott, Alastair A.; Branciard, Cyril; Brukner, Časlav; Chiribella, Giulio; Walther, Philip

doi:10.1103/physrevresearch.3.013093

Cited by 97 publications

(80 citation statements)

References 49 publications

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“…This is in line with the general intuition that this type of divisibility additionally requires weak causal ordering of the dynamics and is thus a more fragile property. This motivates further investigation, for example in relation to recent work on causal ordering in quantum information theory [66,67].…”

Section: Cross-relations Between Heisenberg and Schrödinger Jump Operatorsmentioning

confidence: 79%

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Fermionic duality: General symmetry of open systems with strong dissipation and memory

Bruch

Nestmann

Schulenborg³

et al. 2021

SciPost Phys.

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We consider the exact time-evolution of a broad class of fermionic open quantum systems with both strong interactions and strong coupling to wide-band reservoirs. We present a nontrivial fermionic duality relation between the evolution of states (Schrödinger) and of observables (Heisenberg). We show how this highly nonintuitive relation can be understood and exploited in analytical calculations within all canonical approaches to quantum dynamics, covering Kraus measurement operators, the Choi-Jamiołkowski state, time-convolution and convolutionless quantum master equations and generalized Lindblad jump operators. We discuss the insights this offers into the divisibility and causal structure of the dynamics and the application to nonperturbative Markov approximations and their initial-slip corrections. Our results underscore that predictions for fermionic models are already fixed by fundamental principles to a much greater extent than previously thought.

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Section: Cross-relations Between Heisenberg and Schrödinger Jump Operatorsmentioning

confidence: 79%

“…In neither of the above general relations fermionic duality was used and it is thus important to check that it is consistent with these relations. To see this, substitute (49) and (67) in Eq. (103) to recover Eq.…”

Section: E Fixed-point Relation Generator and Memory Kernelmentioning

confidence: 99%

Fermionic duality: General symmetry of open systems with strong dissipation and memory

Bruch

Nestmann

Schulenborg³

et al. 2021

SciPost Phys.

View full text Add to dashboard Cite

show abstract

“…As counter-intuitive as it seems, the ability of information carrier traversing a superposition of classical trajectories has been experimentally verified using a quantum device called quantum switch [4]- [12]. Until recently, the alluring benefits of the indefinite casual order of quantum process have been reported for various aspects of quantum information processing, including quantum computation [13], [14], noiseless quantum teleportation [15], communication complexity [16], quantum resource theory [17], [18], quantum metrology [19], discrimination of quantum process [20], and ultimately for boosting the channel capacities of quantum and classical communications over quantum channels [21]- [24].…”

Section: Introductionmentioning

confidence: 99%

The Entanglement-Assisted Communication Capacity Over Quantum Trajectories

Chandra

Caleffi

Cacciapuoti

2022

IEEE Trans. Wireless Commun.

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The unique and often-weird properties of quantum mechanics allow an information carrier to propagate through multiple trajectories of quantum channels simultaneously. This ultimately leads us to quantum trajectories with an indefinite causal order of quantum channels. It has been shown that indefinite causal order enables the violation of bottleneck capacity, which bounds the amount of the transferable classical and quantum information through a classical trajectory with a well-defined causal order of quantum channels. In this treatise, we investigate this beneficial property in the realm of both entanglementassisted classical and quantum communications. To this aim, we derive closed-form capacity expressions of entanglement-assisted classical and quantum communication for arbitrary quantum Pauli channels over classical and quantum trajectories. We show that by exploiting the indefinite causal order of quantum channels, we obtain capacity gains over classical trajectory as well as the violation of bottleneck capacity for various practical scenarios. Furthermore, we determine the operating region where entanglement-assisted communication over quantum trajectory obtains capacity gain against classical trajectory and where the entanglement-assisted communication over quantum trajectory violates the bottleneck capacity.

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“…The coherent control of quantum channels generalises the 'if' clause in classical computation to the quantum level, where the use or not of a given quantum channel is determined by the value of another quantum system -enabling the possibility of using multiple quantum channels in a superposition. This idea can be applied equally to computation, where it is often referred to as control of unknown unitaries (or channels) [15,16,17,18,19,20,21] and communication, where it takes the form of communication in a superposition of trajectories [22,23,24,25,26,27,28]. We shall describe superpositions of quantum channels in depth in Section 2.1, focusing on the communication perspective of Ref.…”

Section: Introductionmentioning

confidence: 99%

Routed quantum circuits

Vanrietvelde

Kristjánsson

Barrett

2021

Quantum

Self Cite

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We argue that the quantum-theoretical structures studied in several recent lines of research cannot be adequately described within the standard framework of quantum circuits. This is in particular the case whenever the combination of subsystems is described by a nontrivial blend of direct sums and tensor products of Hilbert spaces. We therefore propose an extension to the framework of quantum circuits, given by routed linear maps and routed quantum circuits. We prove that this new framework allows for a consistent and intuitive diagrammatic representation in terms of circuit diagrams, applicable to both pure and mixed quantum theory, and exemplify its use in several situations, including the superposition of quantum channels and the causal decompositions of unitaries. We show that our framework encompasses the `extended circuit diagrams' of Lorenz and Barrett [arXiv:2001.07774 (2020)], which we derive as a special case, endowing them with a sound semantics.

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Experimental quantum communication enhancement by superposing trajectories

Cited by 97 publications

References 49 publications

Fermionic duality: General symmetry of open systems with strong dissipation and memory

Fermionic duality: General symmetry of open systems with strong dissipation and memory

The Entanglement-Assisted Communication Capacity Over Quantum Trajectories

Routed quantum circuits

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