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Quantum clock synchronization (QCS) aims to establish a shared temporal reference between distant nodes by exploiting uniquely quantum phenomena such as entanglement, single-photon interference, and quantum correlations. In contrast to…

Discrete time-crystals are periodically driven quantum many-body systems with broken discrete-time translational symmetry, a non-equilibrium steady state representing self-organization of motion of quantum particles. Observations of…

Mesoscale and Nanoscale Physics · Physics 2022-06-28 Subhajit Sarkar , Yonatan Dubi

Born in the intersection between quantum mechanics and general relativity, indefinite causal structure is the idea that in the continuum of time, some sets of events do not have an inherent causal order between them. Process matrices,…

Quantum Physics · Physics 2024-10-08 Omri Shmueli

Out-of-time-ordered-correlators (OTOCs) have been suggested as a means to diagnose chaotic behavior in quantum mechanical systems. Recently, it was found that OTOCs display exponential growth for the inverted quantum harmonic oscillator,…

High Energy Physics - Theory · Physics 2024-08-26 Paul Romatschke

Consider a bipartite quantum system with at least one of its two components being itself a composite system. By tracing over part of one (or both) of these two subsystems it is possible to obtain a reduced (separable) state that exhibits…

Quantum Physics · Physics 2015-04-10 Guido Bellomo , Ana P. Majtey , A. R. Plastino , A. Plastino

The quantum teleportation protocol can be used to probabilistically simulate a quantum circuit with backward-in-time connections. This allows us to analyze some conceptual problems of time travel in the context of physically realizable…

Quantum Physics · Physics 2012-03-06 George Svetlichny

Discrete time crystals (DTCs) are new phases of matter characterized by the presence of an observable evolving with $nT$ periodicity under a $T$-periodic Hamiltonian, where $n>1$ is an integer insensitive to small parameter variations. In…

Quantum Physics · Physics 2020-01-17 Pekik Nurwantoro , Raditya Weda Bomantara , Jiangbin Gong

We consider the motion of a gyroscope on a closed timelike curve (CTC). A gyroscope is identified with a unit-length spacelike vector - a spin-vector - orthogonal to the tangent to the CTC, and satisfying the equations of Fermi-Walker…

General Relativity and Quantum Cosmology · Physics 2026-01-23 Brien C. Nolan

Anomaly detection in multi-variate time series (MVTS) data is a huge challenge as it requires simultaneous representation of long term temporal dependencies and correlations across multiple variables. More often, this is solved by breaking…

Machine Learning · Computer Science 2022-02-09 Theivendiram Pranavan , Terence Sim , Arulmurugan Ambikapathi , Savitha Ramasamy

We investigate quantum correlations in time in different approaches. We assume that temporal correlations should be treated in an even-handed manner with spatial correlations. We compare the pseudo-density matrix formalism with several…

Quantum Physics · Physics 2020-12-23 Tian Zhang , Oscar Dahlsten , Vlatko Vedral

In instantaneous nonlocal quantum computation, two parties cooperate in order to perform a quantum computation on their joint inputs, while being restricted to a single round of simultaneous communication. Previous results showed that…

Quantum Physics · Physics 2016-08-24 Anne Broadbent

Entanglement is a fundamental resource for quantum information processing. In its pure form, it allows quantum teleportation and sharing classical secrets. Realistic quantum states are noisy and their usefulness is only partially…

Quantum Physics · Physics 2014-04-15 Maris Ozols , Graeme Smith , John A. Smolin

It is well known that entangled quantum states can be nonlocal: the correlations between local measurements carried out on these states cannot always be reproduced by local hidden variable models. Svetlichny, followed by others, showed that…

Quantum Physics · Physics 2009-11-10 Nick S. Jones , Noah Linden , Serge Massar

Discrete time crystals (DTCs) are nonequilibrium phases of matter characterized by robust subharmonic order parameter dynamics. We report a new type of DTC in a periodically driven surface code, the subharmonic signature of which is only…

Quantum Physics · Physics 2021-08-04 Raditya Weda Bomantara

We study the transition from the full quantum mechanical description of physical systems to an approximate classical stochastic one. Our main tool is the identification of the closed-time-path (CTP) generating functional of Schwinger and…

General Relativity and Quantum Cosmology · Physics 2016-08-31 Charis Anastopoulos

We draw an explicit connection between the statistical properties of an entangled two-mode continuous variable (CV) resource and the amount of entanglement that can be dynamically transferred to a pair of non-interacting two-level systems.…

Quantum Physics · Physics 2015-05-13 Mauro Paternostro , Gerardo Adesso , Steve Campbell

We propose and simulate a protocol to evolve a quantum particle forward in time such that its trajectory closely matches that of the particle's Newtonian counterpart. Using short bursts of Schr\"odinger time-evolution interleaved with…

Quantum Physics · Physics 2025-10-21 Youheng Zheng

Quantum entanglement, perhaps the most non-classical manifestation of quantum information theory, cannot be used to transmit information between remote parties. Yet, it can be used to reduce the amount of communication required to process a…

Quantum Physics · Physics 2015-06-29 Gilles Brassard , Anne Broadbent , Alain Tapp

We address fundamental limitations of quantum teleportation -- the process of transferring quantum information using classical communication and preshared entanglement. We develop a new teleportation protocol based upon the idea of using…

Quantum Physics · Physics 2021-09-01 Patryk Lipka-Bartosik , Paul Skrzypczyk

We study broadband polarization entangled states generated within the line width of type-II Spontaneous Parametric Down Conversion (SPDC). Applying a complete quantum polarization tomography protocol at arbitrary combination of frequency…

Quantum Physics · Physics 2015-05-19 Dmitry A. Kalashnikov , Leonid A. Krivitsky