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3.0

Jun 30, 2018
06/18

by
Jing Zhang; Yu-xi Liu; Re-Bing Wu; Kurt Jacobs; Sahin Kaya Ozdemir; Lan Yang; Tzyh-Jong Tarn; Franco Nori

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Quantum input-output theory plays a very important role for analyzing the dynamics of quantum systems, especially large-scale quantum networks. As an extension of the input-output formalism of Gardiner and Collet, we develop a new approach based on the quantum version of the Volterra series which can be used to analyze nonlinear quantum input-output dynamics. By this approach, we can ignore the internal dynamics of the quantum input-output system and represent the system dynamics by a series of...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1407.8108

3
3.0

Jun 30, 2018
06/18

by
Max R. Atkin; Stefan Zohren

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We consider the expected violations of Bell inequalities from random pure states. More precisely, we focus on a slightly generalised version of the CGLMP inequality, which concerns Bell experiments of two parties, two measurement options and N outcomes and analyse their expected quantum violations from random pure states for varying N, assuming the conjectured optimal measurement operators. It is seen that for small N the Bell inequality is not violated on average, while for larger N it is....

Topics: Quantum Physics, Mathematics, Mathematical Physics

Source: http://arxiv.org/abs/1407.8233

3
3.0

Jun 30, 2018
06/18

by
Salvatore Mandrà; Gian Giacomo Guerreschi; Alán Aspuru-Guzik

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Adiabatic quantum optimization is a procedure to solve a vast class of optimization problems by slowly changing the Hamiltonian of a quantum system. The evolution time necessary for the algorithm to be successful scales inversely with the minimum energy gap encountered during the dynamics. Unfortunately, the direct calculation of the gap is strongly limited by the exponential growth in the dimensionality of the Hilbert space associated to the quantum system. Although many special-purpose...

Topics: Quantum Physics, Physics, Computational Physics, Disordered Systems and Neural Networks, Condensed...

Source: http://arxiv.org/abs/1407.8183

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10.0

Jun 30, 2018
06/18

by
Samuel Colin; Antony Valentini

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We study incomplete relaxation to quantum equilibrium at long wavelengths, during a pre-inflationary phase, as a possible explanation for the reported large-scale anomalies in the cosmic microwave background (CMB). Our scenario makes use of the de Broglie-Bohm pilot-wave formulation of quantum theory, in which the Born probability rule has a dynamical origin. The large-scale power deficit could arise from incomplete relaxation for the amplitudes of the primordial perturbations. We show, by...

Topics: Quantum Physics, High Energy Physics - Theory, Astrophysics, Cosmology and Nongalactic Astrophysics

Source: http://arxiv.org/abs/1407.8262

3
3.0

Jun 30, 2018
06/18

by
Sanjib Dey; Andreas Fring; Thilagarajah Mathanaranjan

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We propose a noncommutative version of the Euclidean Lie algebra $E_2$. Several types of non-Hermitian Hamiltonian systems expressed in terms of generic combinations of the generators of this algebra are investigated. Using the breakdown of the explicitly constructed Dyson maps as a criterium, we identify the domains in the parameter space in which the Hamiltonians have real energy spectra and determine the exceptional points signifying the crossover into the different types of spontaneously...

Topics: Quantum Physics, Mathematics, Mathematical Physics

Source: http://arxiv.org/abs/1407.8097

5
5.0

Jun 30, 2018
06/18

by
Siddharth Karumanchi; Stefano Mancini; Andreas Winter; Dong Yang

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We initiate the study of passive environment-assisted communication via a quantum channel, modeled as a unitary interaction between the information carrying system and an environment. In this model, the environment is controlled by a benevolent helper who can set its initial state such as to assist sender and receiver of the communication link. (The case of a malicious environment, also known as jammer, or arbitrarily varying channel, is essentially well-understood and comprehensively...

Topics: Quantum Physics, Mathematics, Computing Research Repository, Information Theory

Source: http://arxiv.org/abs/1407.8160

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11

Jun 30, 2018
06/18

by
Stefan Ataman

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In this paper we describe a novel, graphical method, allowing the fast computation of field operator transformations for linear lossless optical devices in Quantum Optics (QO). The advantage of this method grows with the complexity of the considered optical setup. As case studies we examine the field operator transformations for the beam splitter (BS), the Mach-Zehnder interferometer (MZI) and the double MZI. We consider the simple case with monochromatic input light, as well as extensions to...

Topics: Physics, Quantum Physics, Optics

Source: http://arxiv.org/abs/1407.8064

6
6.0

Jun 30, 2018
06/18

by
Yan-Lin Tang; Hua-Lei Yin; Si-Jing Chen; Yang Liu; Wei-Jun Zhang; Xiao Jiang; Lu Zhang; Jian Wang; Li-Xing You; Jian-Yu Guan; Dong-Xu Yang; Zhen Wang; Hao Liang; Zhen Zhang; Nan Zhou; Xiongfeng Ma; Teng-Yun Chen; Qiang Zhang; Jian-Wei Pan

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Measurement-device-independent quantum key distribution (MDIQKD) protocol is immune to all attacks on detection and guarantees the information-theoretical security even with imperfect single photon detectors. Recently, several proof-of-principle demonstrations of MDIQKD have been achieved. Those experiments, although novel, are implemented through limited distance with a key rate less than 0.1 bps. Here, by developing a 75 MHz clock rate fully-automatic and highly-stable system, and...

Topic: Quantum Physics

Source: http://arxiv.org/abs/1407.8012