Frontiers of quantum physics

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Phase-preserving linear amplifiers not simulable by the parametric amplifier

(2019)

Authors:

A Chia, M Hajdusek, R Nair, R Fazio, LC Kwek, V Vedral

Different instances of time as different quantum modes: quantum states across space-time for continuous variables

(2019)

Authors:

Tian Zhang, Oscar Dahlsten, Vlatko Vedral

Wavevector distribution of metal photoluminescence from a gold film coupled microsphere antenna

Journal of Optics 21 (3), 035002

Authors:

Adarsh B Vasista, Sunny Tiwari, GV Pavan Kumar

Abstract:

Engineering statistical transmutation of identical quantum particles

PHYSICAL REVIEW B 99:4 (2019) ARTN 045430

Authors:

Simone Barbarino, Rosario Fazio, Vlatko Vedral, Yuval Gefen

Theoretical description and experimental simulation of quantum entanglement near open time-like curves via pseudo-density operators

Nature Communications Springer Nature 10 (2019) 182

Authors:

Chiara Marletto, Vlatko Vedral, S Virz矛, E Rebufello, A Avella, F Piacentini, M Gramegna, IP Degiovanni, M Genovese

Abstract:

Closed timelike curves are striking predictions of general relativity allowing for time-travel. They are afflicted by notorious causality issues (e.g. grandfather's paradox). Quantum models where a qubit travels back in time solve these problems, at the cost of violating quantum theory's linearity-leading e.g. to universal quantum cloning. Interestingly, linearity is violated even by open timelike curves (OTCs), where the qubit does not interact with its past copy, but is initially entangled with another qubit. Non-linear dynamics is needed to avoid violating entanglement monogamy. Here we propose an alternative approach to OTCs, allowing for monogamy violations. Specifically, we describe the qubit in the OTC via a pseudo-density operator-a unified descriptor of both temporal and spatial correlations. We also simulate the monogamy violation with polarization-entangled photons, providing a pseudo-density operator quantum tomography. Remarkably, our proposal applies to any space-time correlations violating entanglement monogamy, such as those arising in black holes.