Witnessing nonclassicality beyond quantum theory
Physical Review D American Physical Society (APS) 102:8 (2020) 086012
Machine learning meets quantum foundations: A brief survey
AVS Quantum Science American Vacuum Society 2:3 (2020) 034101
Phase-Preserving Linear Amplifiers Not Simulable by the Parametric Amplifier.
Physical review letters 125:16 (2020) 163603
Abstract:
It is commonly accepted that a parametric amplifier can simulate a phase-preserving linear amplifier regardless of how the latter is realized [C. M. Caves et al., Phys. Rev. A 86, 063802 (2012)PLRAAN1050-294710.1103/PhysRevA.86.063802]. If true, this reduces all phase-preserving linear amplifiers to a single familiar model. Here we disprove this claim by constructing two counterexamples. A detailed discussion of the physics of our counterexamples is provided. It is shown that a Heisenberg-picture analysis facilitates a microscopic explanation of the physics. This also resolves a question about the nature of amplifier-added noise in degenerate two-photon amplification.Quantum Refrigeration with Indefinite Causal Order.
Physical review letters 125:7 (2020) 070603
Abstract:
We propose a thermodynamic refrigeration cycle which uses indefinite causal orders to achieve nonclassical cooling. The cycle cools a cold reservoir while consuming purity in a control qubit. We first show that the application to an input state of two identical thermalizing channels of temperature T in an indefinite causal order can result in an output state with a temperature not equal to T. We investigate the properties of the refrigeration cycle and show that thermodynamically, the result is compatible with unitary quantum mechanics in the circuit model but could not be achieved classically. We believe that this cycle could be implemented experimentally using tabletop photonics. Our result suggests the development of a new class of thermodynamic resource theories in which operations are allowed to be performed in an indefinite causal order.Aharonov-Bohm Phase is Locally Generated Like All Other Quantum Phases.
Physical review letters 125:4 (2020) 040401