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Jun 29, 2018
06/18

by
Wei Wu; Hai-Qing Lin

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We report an anomalous decoherence phenomenon of a quantum dissipative system in the framework of a stochastic decoupling scheme along with a hierarchical equations-of-motion formalism without the usual Born-Markov or weak coupling approximations. It is found that the decoherence of a two-qubit spin-boson model can be reduced by increasing the bath temperature in strong-coupling regimes. For the weak-coupling situation, we find that the bath temperature may enhance the decoherence. This result...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1612.05338

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Jun 29, 2018
06/18

by
Ritajit Majumdar; Saikat Basu; Priyanka Mukhopadhyay; Susmita Sur-Kolay

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Descriptions of quantum algorithms, communication etc. protocols assume the existence of closed quantum system. However, real life quantum systems are open and are highly sensitive to errors. Hence error correction is of utmost importance if quantum computation is to be carried out in reality. Ideally, an error correction block should be placed after every gate operation in a quantum circuit. This increases the overhead and reduced the speedup of the quantum circuit. Moreover, the error...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1612.08044

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Jun 30, 2018
06/18

by
Marjan Jafari; Fardin Kheirandish

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The quantum dynamics of a damped harmonic oscillator is investigated in the presence of an anisotropic heat bath. The medium is modeled by a continuum of three dimensional harmonic oscillators and anisotropic coupling is treated by introducing tensor coupling functions. Starting from a classical Lagrangian, the total system is quantized in the framework of the canonical quantization. Following Fano technique, Hamiltonian of the system is diagonalized in terms of creation and annihilation...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1701.00964

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4.0

Jun 30, 2018
06/18

by
Swathi S Hegde

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Feynman, in 1982, proposed the idea of using a quantum simulator to perform quantum simulations. A quantum simulator is basically a controllable quantum system that can mimic the dynamics of other quantum systems we wish to study. In this thesis we investigate some aspects of quantum simulation using both unitary and nonunitary controls. In the unitary part, we experimentally simulated the phenomenon of quantum many-body freezing, and also developed a general protocol to decompose an arbitrary...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1701.03443

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Jun 30, 2018
06/18

by
Jennifer C. J. Radtke; Daniel K. L. Oi; John Jeffers

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The bosonic nature of light leads to counter-intuitive bunching effects. We describe an experimentally testable effect in which a single photon is induced through a highly reflecting beamsplitter by a large amplitude coherent state, with probability 1/e in the limit of large coherent state amplitude. We use this effect to construct a viable implementation of the bare raising operator on coherent states via conditional measurement, which succeeds with high probability and fidelity even in the...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1701.04251

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5.0

Jun 30, 2018
06/18

by
Vincent Camus

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This report is a synthesis of my master thesis internship at the National Institute of Informatics (NII) in Tokyo, Japan, that lasted during the summer of year 2012. I worked in the Quantum Information Science Theory (QIST) group under supervision of Prof. Kae Nemoto and Dr. Simon Devitt. This group works on theoretical and experimental implementations of quantum information science. The aim of my project was to study and improve quantum optical systems. I first studied different fields and...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1702.06530

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4.0

Jun 30, 2018
06/18

by
C. Marques; GS Dias; FC Khanna; Helder S. Chavez

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The supersymmetry breaking in a supersymmetric harmonic oscillator from interaction and at finite temperature is analyzed. Due to the additivity of the thermal effects, the restored supersymmetry through this polynomial interaction, results in nonvanishing energy at finite temperatures while at T = 0 the energy is zero.

Topic: Quantum Physics

Source: http://arxiv.org/abs/1703.03820

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Jun 29, 2018
06/18

by
David Hocker; Julia Yan; Herschel Rabitz

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Bose-Einstein condensates (BECs) offer the potential to examine quantum behavior at large length and time scales, as well as forming promising candidates for quantum technology applications. Thus, the manipulation of BECs using control fields is a topic of prime interest. We consider BECs in the mean field model of the Gross-Pitaevskii equation (GPE), which contains linear and nonlinear features, both of which are subject to control. In this work we report successful optimal control simulations...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1603.08475

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Jun 29, 2018
06/18

by
Toby S. Cubitt; David Perez-Garcia; Michael M. Wolf

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The aim of this short note is to clarify some of the claims made in the comparison made in [S. Lloyd, On the uncomputability of the spectral gap, arXiv:1602.05924] between our recent result [T.S. Cubitt, D. Perez-Garcia, M.M. Wolf, Undecidability of the spectral gap, Nature 528, 207-211 (2015), arXiv:1502.04573] and his 1994 paper [S. Lloyd, Necessary and sufficient conditions for quantum computation, J. Mod. Opt. 41(12), 2503-2520 (1994)].

Topic: Quantum Physics

Source: http://arxiv.org/abs/1603.00825

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Jun 29, 2018
06/18

by
Andrea Beggi; Luca Razzoli; Paolo Bordone

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We study the dynamics and the entanglement between two interacting identical bosons performing a quantum walk on a 1D lattice. The system is described by the Hubbard model, and the interaction among the particles can be either attractive or repulsive. We show that there are clear signatures - both in the evolution and in the correlations - that allow a distinction between the two cases, and we demonstrate that these features result to be intimately connected with the bandstructure and the...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1605.07513

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Jun 29, 2018
06/18

by
Marco G. Genoni; O. S. Duarte; A. Serafini

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Inspired by the notion that environmental noise is in principle observable, whilst fundamental noise due to spontaneous localisation would not be, we study the estimation of the diffusion parameter induced by wave function collapse models under continuous monitoring of the environment. We take into account finite measurement efficiencies and, in order to quantify the advantage granted by monitoring, we analyse the quantum Fisher information associated with such a diffusion parameter, identify...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1605.09168

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Jun 29, 2018
06/18

by
Sam McMillen; Matteo Brunelli; Matteo Carlesso; Angelo Bassi; Hendrik Ulbricht; Matteo G. A. Paris; Mauro Paternostro

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We apply the formalism of quantum estimation theory to extract information about potential collapse mechanisms of the continuous spontaneous localisation (CSL) form. In order to estimate the strength with which the field responsible for the CSL mechanism couples to massive systems, we consider the optomechanical interaction between a mechanical resonator and a cavity field. Our estimation strategy passes through the probing of either the state of the oscillator or that of the electromagnetic...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.00070

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6.0

Jun 29, 2018
06/18

by
D. Sokolovski; L. M. Baskin

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For a number of non-interacting identical particles entering a multi-channel scatterer in various wave packet states, we construct a generating function for the probabilities of various scattering outcomes. This is used to evaluate the mean numbers of particles $\overline{n}_m$ scattered into a given ($m$-th) channel, single-channel statistics, and inter-channel correlations. We show that for initially uncorrelated particles, indistinguishability changes single channel statistics without...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.06549

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Jun 29, 2018
06/18

by
John M. Myers; F. Hadi Madjid

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A clock steps a computer through a cycle of phases. For the propagation of logical symbols from one computer to another, each computer must mesh its phases with arrivals of symbols from other computers. Even the best atomic clocks drift unforeseeably in frequency and phase; feedback steers them toward aiming points that depend on a chosen wave function and on hypotheses about signal propagation. A wave function, always under-determined by evidence, requires a guess. Guessed wave functions are...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.07723

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Jun 29, 2018
06/18

by
Paolo Solinas; Simone Gasparinetti

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What is the role of coherence in determining the distribution of work done on a quantum system? We approach this question from an operational perspective and consider a setup in which the internal energy of a closed system is recorded by a quantum detector before and after the system is acted upon by an external drive. We find that the resulting work distribution depends on the initial state of the detector as well as on the choice of the final measurement. We consider two complementary...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.08633

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4.0

Jun 29, 2018
06/18

by
Y. -H. Lien; G. Barontini; M. Scheucher; M. Mergenthaler; J. Goldwin; E. A. Hinds

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It is usually considered that the spectrum of an optical cavity coupled to an atomic medium does not exhibit a normal-mode splitting unless the system satisfies the strong coupling condition, meaning the Rabi frequency of the coherent coupling exceeds the decay rates of atom and cavity excitations. Here we show that this need not be the case, but depends on the way in which the coupled system is probed. Measurements of the reflection of a probe laser from the input mirror of an overdamped...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1607.02362

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5.0

Jun 29, 2018
06/18

by
Michael Jarret; Stephen P. Jordan; Brad Lackey

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Most experimental and theoretical studies of adiabatic optimization use stoquastic Hamiltonians, whose ground states are expressible using only real nonnegative amplitudes. This raises a question as to whether classical Monte Carlo methods can simulate stoquastic adiabatic algorithms with polynomial overhead. Here, we analyze diffusion Monte Carlo algorithms. We argue that, based on differences between L1 and L2 normalized states, these algorithms suffer from certain obstructions preventing...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1607.03389

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5.0

Jun 29, 2018
06/18

by
J. Lugani; C. Banerjee; M-A. Maynard; P. Neveu; W. Xie; R. Ghosh; F. Bretenaker; F. Goldfarb

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We report our experimental results on phase-sensitive amplification (PSA) in non-degenerate signal-idler configuration using ultra-narrow coherent population oscillations in metastable helium at room temperature. We achieved a high PSA gain of nearly 7 with a bandwidth of 200 kHz, by using the system at resonance in a single-pass scheme. Further, the measured minimum gain is close to the ideal value, showing that we have a pure PSA. This is also confirmed from our phase-to-phase transfer curves...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1608.00907

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5.0

Jun 29, 2018
06/18

by
Xuefeng Duan; Chi-Kwong Li; Diane Christine Pelejo

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We use projection methods to construct (global) quantum states with prescribed reduced (marginal) states, and possibly with some special properties such as having specific eigenvalues, having specific rank and extreme von Neumann or R\'{e}nyi entropy. Using convex analysis, optimization techniques on matrix manifolds, we obtain algorithms to solve the problem. Matlab programs are written based on these algorithms and numerical examples are illustrated. The numerical results reveal new patterns...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1604.08289

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5.0

Jun 29, 2018
06/18

by
Miquel Montero

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In this Chapter, we present some interesting properties of quantum walks on the line. We concentrate our attention in the emergence of invariance and provide some insights into the ultimate origin of the observed behavior. In the first part of the Chapter, we review the building blocks of the quantum-mechanical version of the standard random walk in one dimension. The most distinctive difference between random and quantum walks is the replacement of the random coin in the former by the action...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.06156

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Jun 29, 2018
06/18

by
J. Sperling; T. J. Bartley; G. Donati; M. Barbieri; X. -M. Jin; A. Datta; W. Vogel; I. A. Walmsley

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We study, in theory and experiment, the quantum properties of correlated light fields measured with click-counting detectors providing incomplete information on the photon statistics. We establish a correlation parameter for the conditional statistics, and we derive the corresponding nonclassicality criteria for detecting conditional quantum correlations. Classical bounds for Pearson's correlation parameter are formulated that allow us, once they are violated, to determine nonclassical...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1603.01389

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5.0

Jun 29, 2018
06/18

by
T. J. Volkoff

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We derive families of optimal and near-optimal probe states for quantum estimation of the coupling constants of a general two-mode number-conserving bosonic Hamiltonian describing one-body and two-body dynamics. We find that the optimal states for estimating the dephasing of the modes, the self-interaction strength, and the contact interaction strength are related to the NOON states, whereas the optimal states for estimation of the intermode single particle tunneling amplitude are...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1610.05807

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5.0

Jun 29, 2018
06/18

by
Kaifeng Bu; Heng Fan; Arun Kumar Pati; Junde Wu

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We propose the resource theory of a special antiunitary asymmetry in quantum theory. The notion of antiunitary asymmetry, in particular, ${\cal PT}$-asymmetry is different from the usual resource theory for asymmetry about unitary representation of a symmetry group, as the ${\cal PT}$ operator is an antiunitary operator with ${\cal P}$ being any self-inverse unitary and ${\cal T}$ being the time-reversal operations. Here, we introduce the ${\cal PT}$-symmetric states, ${\cal PT}$-covariant...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1610.09646

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7.0

Jun 29, 2018
06/18

by
Ángel Rivas

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We study the properties of a refined weak coupling limit that preserves complete positivity in order to describe non-Markovian dynamics in the spin-boson model. With this tool, we show the system presents a rich and new non-Markovian phenomenology. This implies a dynamical difference between entanglement and coherence: the latter undergoes revivals whereas the former not, despite the induced dynamics being fully incoherent. In addition, the evolution presents "quasieternal"...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1611.01483

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Jun 29, 2018
06/18

by
A. Y. Klimenko

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When applied to matter and antimatter states, the Pauli master equation (PME) may have two forms: time-symmetric, which is conventional, and time-antisymmetric, which is suggested in the present work. The symmetric and antisymmetric forms correspond to symmetric and antisymmetric extensions of thermodynamics from matter to antimatter --- this is demonstrated by proving the corresponding H-theorem. The two forms are based on the thermodynamic similarity of matter and antimatter and differ only...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1611.04582

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4.0

Jun 29, 2018
06/18

by
H. R. Reiss

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It is shown that electromagnetic potentials convey physical information beyond that supplied by electric and magnetic fields alone, and are thus more fundamental. Observable physical properties can impose conditions on the selection of electromagnetic gauge (i.e. sets of potentials) that are explicit and restrictive. This is true both classically and quantum mechanically. The implication that the choice of gauge carries physical information is confirmed by exhibiting a set of potentials that...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1609.03420

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7.0

Jun 29, 2018
06/18

by
B. Opanchuk; L. Rosales-Zárate; R. Y. Teh; M. D. Reid

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We examine how to signify and quantify the mesoscopic quantum coherence of approximate two-mode NOON states and spin-squeezed two-mode Bose-Einstein condensates (BEC). We identify two criteria that verify a nonzero quantum coherence between states with quantum number different by $n$. These criteria negate certain mixtures of quantum states, thereby signifying a generalised $n$-scopic Schrodinger cat-type paradox. The first criterion is the correlation $\langle\hat{a}^{\dagger...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1609.06028

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6.0

Jun 29, 2018
06/18

by
Chyi-Lung Lin

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Ehrenfest's theorem in the infinite square well is up to now only manifested indirectly. The manifestation of this theorem is first done in the finite square well, and then consider the infinite square well as the limit of the finite well. For a direct manifestation, we need a more precise formula to describe the degree of infiniteness of the divergent potential energy. We show that the potential energy term term, which is the product of the potential energy and the energy eigenfunction, is a...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1609.07380

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Jun 29, 2018
06/18

by
Keyu Xia; Jason Twamley

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Quantum information processing with hybrid protocols making use of discrete- and continuous-variable currently attracts of great interest because of its promising applications in scalable quantum computer and distant quantum network. By inducing a giant cross-Kerr nonlinearity between two cavities, we propose a general protocol for hybrid quantum gate and quantum entanglement with high fidelity between a stationary, discrete photonic qubit and a flying photonic state. Interestingly, our...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1610.03556

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Jun 29, 2018
06/18

by
Fabian Furrer; William J. Munro

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Optical telecommunication is at the heart of today's internet and is currently enabled by the transmission of intense optical signals between remote locations. As we look to the future of telecommunication, quantum mechanics promise new ways to be able to transmit and process that information. Demonstrations of quantum key distribution and quantum teleportation using multi-photon states have been performed, but only over ranges limited to one hundred kilometers. To go beyond this, we need...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1611.02795

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Jun 29, 2018
06/18

by
Friederike Anna Dziemba

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Using the tool of concatenated stabilizer coding, we prove that the complexity class QMA remains unchanged even if every witness qubit is disturbed by constant noise. This result may not only be relevant for physical implementations of verifying protocols but also attacking the relationship between the complexity classes QMA, QCMA and BQP, which can be reformulated in this unified framework of a verifying protocol receiving a disturbed witness. While QCMA and BQP are described by fully...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1611.07332

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Jun 29, 2018
06/18

by
Nikita Vostrosablin; Andrey A. Rakhubovsky; Radim Filip

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Feasible setup for pulsed quantum non-demolition interaction between two distant mechanical oscillators through optical or microwave mediator is proposed. The proposal uses homodyne measurement of the mediator and feedforward control of the mechanical oscillators to reach the interaction. To verify quantum nature of the interaction, we investigate the Gaussian entanglement generated in the mechanical modes. We evaluate it under influence of mechanical bath and propagation loss for the mediator...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1605.05932

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3.0

Jun 29, 2018
06/18

by
Ville Bergholm; F. K. Wilhelm; T. Schulte-Herbrueggen

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We study reachable sets of open n-qubit quantum systems, whose coherent parts are under full unitary control, by adding as a further degree of incoherent control switchable Markovian noise on a single qubit. In particular, adding bang-bang control of amplitude damping noise (non-unital) allows the dynamic system to act transitively on the entire set of density operators. Thus one can transform any initial quantum state into any desired target state. Adding switchable bit-flip noise (unital)...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1605.06473

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3.0

Jun 29, 2018
06/18

by
Ram Narayan Deb

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We propose a total measure of multi-particle quantum correlation in a system of N two-level atoms (N qubits). We construct a parameter that encompasses all possible quantum correlations among N two-level atoms in arbitrary symmetric pure states and define its numerical value to be the total measure of the net atom-atom correlations. We use that parameter to quantify the total quantum correlations in atomic Schr\"{o}dinger cat states, which are generated by the dispersive interaction in a...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1605.06832

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Jun 29, 2018
06/18

by
Alex Bocharov

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Metaplectic quantum basis is a universal multi-qutrit quantum basis, formed by the ternary Clifford group and the axial reflection gate $R=|0\rangle \langle 0| + |1\rangle \langle 1| - |2\rangle \langle 2|$. It is arguably, a ternary basis with the simplest geometry. Recently Cui, Kliuchnikov, Wang and the Author have proposed a compilation algorithm to approximate any two-level Householder reflection to precision $\varepsilon$ by a metaplectic circuit of $R$-count at most $C \,...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.02315

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Jun 29, 2018
06/18

by
Zi-Wen Liu; Xueyuan Hu; Seth Lloyd

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Resource theory is a widely-applicable framework for analyzing the physical resources required for given tasks, such as computation, communication, and energy extraction. In this paper, we propose a general scheme for analyzing resource theories based on resource destroying maps, which leave resource-free states unchanged but erase the resource stored in all other states. We introduce a group of general conditions that determine whether a quantum operation exhibits typical resource-free...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.03723

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Jun 29, 2018
06/18

by
Christopher J. Pugh; Piotr Kolenderski; Carmelo Scarcella; Alberto Tosi; Thomas Jennewein

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Correlated photon pairs produced by a spontaneous parametric down conversion (SPDC) process can be used for secure quantum communication over long distances including free space transmission over a link through turbulent atmosphere. We experimentally investigate the possibility to utilize the intrinsic strong correlation between the pump and output photon spatial modes to mitigate the negative targeting effects of atmospheric beam wander. Our approach is based on a demonstration observing the...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.04110

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Jun 29, 2018
06/18

by
Hamid Reza Naeij; Afshin Shafiee

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In this study, we solve analytically the Schrodinger equation for a macroscopic quantum oscillator as a central system coupled to two environmental micro-oscillating particles. Then, the double-slit interference patterns are investigated in two limiting cases, considering the limits of uncertainty in the position probability distribution. Moreover, we analyze the interference patterns based on a recent proposal called stochastic electrodynamics with spin. Our results show that when the quantum...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.04462

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Jun 29, 2018
06/18

by
Felix Tennie; Vlatko Vedral; Christian Schilling

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The role of the generalized Pauli constraints (GPCs) in higher spatial dimensions and by incorporating spin degrees of freedom is systematically explored for a system of interacting fermions confined by a harmonic trap. Physical relevance of the GPCs is confirmed by analytical means for the ground state in the regime of weak couplings by finding its vector of natural occupation numbers close to the boundary of the allowed region. Such quasipinning is found to become weaker in the intermediate...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.05334

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Jun 29, 2018
06/18

by
Maurice de Gosson; Basil Hiley; Eliahu Cohen

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The experimental results of Kocsis et al., Mahler et al. and the proposed experiments of Morley et al. show that it is possible to construct "trajectories" in interference regions in a two-slit interferometer. These results call for a theoretical re-appraisal of the notion of a "quantum trajectory" first introduced by Dirac and in the present paper we re-examine this notion from the Bohm perspective based on Hamiltonian flows. In particular, we examine the short-time...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.06065

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Jun 29, 2018
06/18

by
Murphy Yuezhen Niu; Feihu Xu; Fabian Furrer; Jeffrey H. Shapiro

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Time-energy high-dimensional quantum key distribution (HD-QKD) leverages the high-dimensional nature of time-energy entangled biphotons and the loss tolerance of single-photon detection to achieve long-distance key distribution with high photon information efficiency. To date, the general-attack security of HD-QKD has only been proven in the asymptotic regime, while HD-QKD's finite-key security has only been established for a limited set of attacks. Here we fill this gap by providing a rigorous...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.08394

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Jun 29, 2018
06/18

by
Jeremy Ribeiro; Le Phuc Thinh; Jedrzej Kaniewski; Jonas Helsen; Stephanie Wehner

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Quantum communication has demonstrated its usefulness for quantum cryptography far beyond quantum key distribution. One domain is two-party cryptography, whose goal is to allow two parties who may not trust each other to solve joint tasks. Another interesting application is position-based cryptography whose goal is to use the geographical location of an entity as its only identifying credential. Unfortunately, security of these protocols is not possible against an all powerful adversary....

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.08750

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Jun 29, 2018
06/18

by
Adrien Feix; Časlav Brukner

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The constraints arising for a general set of causal relations, both classically and quantumly, are still poorly understood. As a step in exploring this question, we consider a coherently controlled superposition of "direct-cause" and "common-cause" relationships between two events. We propose an implementation involving the spatial superposition of a mass and general relativistic time dilation. Finally, we develop a computationally efficient method to distinguish such...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.09241

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Jun 29, 2018
06/18

by
Bryan T. Gard; Dong Li; Chenglong You; Kaushik P. Seshadreesan; Richard Birrittella; Jerome Luine; Seyed Mohammad Hashemi Rafsanjani; Mohammad Mirhosseini; Omar S. Magaña-Loaiza; Benjamin E. Koltenbah; Claudio G. Parazzoli; Barbara A. Capron; Robert W. Boyd; Christopher C. Gerry; Hwang Lee; Jonathan P. Dowling

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Probabilistic amplification through photon addition, at the output of an Mach-Zehnder interferometer is discussed for a coherent input state. When a metric of signal to noise ratio is considered, nondeterministic, noiseless amplification of a coherent state shows improvement over a standard coherent state, for the general addition of $m$ photons. The efficiency of realizable implementation of photon addition is also considered and shows how the collected statistics of a post selected state,...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1606.09598

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Jun 29, 2018
06/18

by
Eylee Jung; DaeKil Park

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We introduce two tangle-based four-party entanglement measures $t_1$ and $t_2$, and two negativity-based measures $n_1$ and $n_2$, which are derived from the monogamy relations. These measures are computed for three four-qubit maximally entangled and W states explicitly. We also compute these measures for the rank-$2$ mixture $\rho_4 = p \ket{\mbox{GHZ}_4} \bra{\mbox{GHZ}_4} + (1 - p) \ket{\mbox{W}_4} \bra{\mbox{W}_4}$ by finding the corresponding optimal decompositions. It turns out that $t_1...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1607.00135

3
3.0

Jun 29, 2018
06/18

by
Albert Benseny; David Tena; Xavier Oriols

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In this paper, the classical Schr\"odinger equation, which allows the study of classical dynamics in terms of wave functions, is analyzed theoretically and numerically. First, departing from classical (Newtonian) mechanics, and assuming an additional single-valued condition for the Hamilton's principal function, the classical Schr\"odinger equation is obtained. This additional assumption implies inherent non-classical features on the description of the dynamics obtained from the...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1607.00168

3
3.0

Jun 29, 2018
06/18

by
Yunlong Xiao; Naihuan Jing; Xianqing Li-Jost

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In Hall's reformulation of the uncertainty principle, the entropic uncertainty relation occupies a core position and provides the first nontrivial bound for the information exclusion principle. Based upon recent developments on the uncertainty relation, we present new bounds for the information exclusion relation using majorization theory and combinatoric techniques, which reveal further characteristic properties of the overlap matrix between the measurements.

Topic: Quantum Physics

Source: http://arxiv.org/abs/1607.00465

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6.0

Jun 29, 2018
06/18

by
R. Esteban Goetz; Maximilian Merkel; Antonia Karamatskou; Robin Santra; Christiane P. Koch

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Photoionization with attosecond pulses populates hole states in the photoion. Superpositions of hole states represent ideal candidates for time-dependent spectroscopy, for example via pump-probe studies. The challenge consists in identifying pulses that create coherent superpositions of hole states while satisfying practical constraints. Here, we employ quantum optimal control to maximize the degree of coherence between these hole states. To this end, we introduce a derivative-free optimization...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1607.02309

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5.0

Jun 29, 2018
06/18

by
O. de los Santos-Sánchez; C. González-Gutiérrez; J. Récamier

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In this work we examine a nonlinear version of the Jaynes-Cummings model for two identical two-level atoms allowing for Ising-like and dipole-dipole interplays between them. The model is said to be nonlinear in the sense that it can incorporate both a general intensity-dependent interaction between the atomic system and the cavity field and/or the presence of a nonlinear medium inside the cavity. As an example, we consider a particular type of atom-field coupling based upon the so-called...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1607.03216

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Jun 29, 2018
06/18

by
Qi Wei; Yudong Cao; Sabre Kais; Bretislav Friedrich; Dudley Herschbach

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We investigate several aspects of realizing quantum computation using entangled polar molecules in pendular states. Quantum algorithms typically start from a product state |00...0> and we show that up to a negligible error, the ground states of polar molecule arrays can be considered as the unentangled qubit basis state |00...0>. This state can be prepared by simply allowing the system to reach thermal equilibrium at low temperature (

Topic: Quantum Physics

Source: http://arxiv.org/abs/1607.04959