The main purpose of this short article is to give a brief overview of the development of the very interesting weak measurement protocol. I add some comments relating to the reality of weak values, and also comment on the allowed values of observables between measurements.

We study the mean Uhlmann curvature in fermionic systems undergoing a dissipative driven phase transition. We consider a paradigmatic class of lattice fermion systems in non-equilibrium steady-state of an open system with local reservoirs, which are characterised by a Gaussian fermionic steady state. In the thermodynamical limit, in systems with translational invariance we show that a singular behaviour of the Uhlmann curvature represents a sufficient criterion for criticalities, in the sense of diverging correlation length, and it is not otherwise sensitive to the closure of the Liouvillian dissipative gap. In finite size systems, we show that the scaling behaviour of the mean Uhlmann curvature maps faithfully the phase diagram, and a relation to the dissipative gap is put forward. We argue that the mean Uhlmann phase can shade light upon the nature of non equilibrium steady state criticality in particular with regard to the role played by quantum vs classical fluctuations.

The question concerning the physical realizability of a probability distribution is of quite importance in Quantum foundations. Specker first pointed out that this question cannot be answered from Kolmogorov's axioms alone. Lately, this observation of Specker has motivated simple principles (exclusivity principle/ local orthogonality principle) that can explain quantum limit regarding the possible sets of experimental probabilities in various nonlocality and contextuality experiments. We study Specker's observation in the simplest scenario involving three inputs each with two outputs. Then using only linear constraints imposed on joint probabilities by this principle, we reveal unphysical nature of Garg-Mermin (GM) correlation. Interestingly, GM correlation was proposed to falsify the following suggestion by Fine: if the inequalities of Clauser and Horne (CH) holds, then there exists a deterministic local hidden-variable model for a spin-1/2 correlation experiment of the Einstein-Podolsky-Rosen type, even when more than two observables are involved on each side. Our result establishes that, unlike in the CH scenario, the local orthogonality principle at single copy level is not equivalent to the no-signaling condition in the GM scenario.

We consider two identical bosons propagating on a one-dimensional lattice and address the prob- lem of discriminating whether their mutual on-site interaction is attractive or repulsive. We suggest a probing scheme based on the properties of the corresponding two-particle quantum walks, and show that the sign of the interaction introduces specific and detectable features in the dynamics of quantum correlations, thus permitting to discriminate between the two cases. We also discuss how these features are connected to the band-structure of the Hubbard Hamiltonian, and prove that discrimination may be obtained only when the two walkers are initially prepared in a superposition of localized states.

Author(s): M. Martinez-Dorantes, W. Alt, J. Gallego, S. Ghosh, L. Ratschbacher, Y. Völzke, and D. Meschede

We demonstrate the parallel and nondestructive readout of the hyperfine state for optically trapped Rb87 atoms. The scheme is based on state-selective fluorescence imaging and achieves detection fidelities >98% within 10 ms, while keeping 99% of the atoms trapped. For the readout of dense arrays ...

[Phys. Rev. Lett. 119, 180503] Published Mon Oct 30, 2017

Author(s): Minho Kwon, Matthew F. Ebert, Thad G. Walker, and M. Saffman

We demonstrate low-loss measurement of the hyperfine ground state of rubidium atoms by state dependent fluorescence detection in a dipole trap array of five sites. The presence of atoms and their internal states are minimally altered by utilizing circularly polarized probe light and a strictly contr...

[Phys. Rev. Lett. 119, 180504] Published Mon Oct 30, 2017

Author(s): Alexander Streltsov, Gerardo Adesso, and Martin B. Plenio

The dictum that “information is physical” indicates that we should understand how features of quantum physics, in particular, the phenomenon of quantum coherence, can be understood to be, and quantified as, a resource for the processing of information. This Colloquium discusses how to characterize, quantify, and manipulate quantum coherence, in application areas ranging from many-body and solid state physics to biological and nanoscale systems.

[Rev. Mod. Phys. 89, 041003] Published Mon Oct 30, 2017

Author(s): H. S. Ku, J. L. Long, X. Wu, M. Bal, R. E. Lake, Edwin Barnes, Sophia E. Economou, and D. P. Pappas

It has been known since the early days of quantum mechanics that hyperbolic secant pulses possess the unique property that they can perform full-cycle Rabi oscillations on two-level quantum systems independently of the pulse detuning. More recently, it was realized that they induce detuning-controll...

[Phys. Rev. A 96, 042339] Published Mon Oct 30, 2017

Author(s): Hongyi Chen, Fan Zhang, Dongxing Zhao, Junxiang Zhang, Jingping Xu, Qiongyi He, Qihuang Gong, and Ying Gu

We theoretically propose a mechanism for the enhancement of quantum field entanglement generated by four-wave mixing through anisotropic Purcell factors in a three-level atomic system. With anisotropic Purcell factors, the dependence of the entanglement on the relative polarization direction between...

[Phys. Rev. A 96, 043865] Published Mon Oct 30, 2017

Author(s): Konstantin B. Yushkov, Vladimir Ya. Molchanov, Andrey V. Ovchinnikov, and Oleg V. Chefonov

Precisely controlled sequences of ultrashort laser pulses are required in various scientific and engineering applications. We developed a phase-only acousto-optic pulse shaping method for replication of ultrashort laser pulses in a TW laser system. A sequence of several Fourier-transform-limited pul...

[Phys. Rev. A 96, 043866] Published Mon Oct 30, 2017

Author(s): Anand Bahl, Jared K. Wahlstrand, Sina Zahedpour, Howard M. Milchberg, and Miroslav Kolesik

The nonlinear polarization response and plasma generation produced by intense optical pulses, modeled by the metastable-electronic-state approach, are verified against space-and-time resolved measurements with single-shot supercontinuum spectral interferometry. This first of a kind theory-experiment...

[Phys. Rev. A 96, 043867] Published Mon Oct 30, 2017

Author(s): Mark J. Ablowitz and Justin T. Cole

A systematic approach for deriving tight-binding approximations in general longitudinally driven lattices is presented. As prototypes, honeycomb and staggered square lattices are considered. Time-reversal symmetry is broken by varying and/or rotating the waveguides, longitudinally, along the directi...

[Phys. Rev. A 96, 043868] Published Mon Oct 30, 2017

Author(s): Tiago J. Arruda, Romain Bachelard, John Weiner, Sebastian Slama, and Philippe W. Courteille

We analytically study the spontaneous emission of a single optical dipole emitter in the vicinity of a plasmonic nanoshell, based on the Lorenz-Mie theory. We show that the fluorescence enhancement due to the coupling between optical emitter and sphere can be tuned by the thickness ratio of the core...

[Phys. Rev. A 96, 043869] Published Mon Oct 30, 2017

Author(s): S. V. Remizov, A. A. Zhukov, D. S. Shapiro, W. V. Pogosov, and Yu. E. Lozovik

We consider a dissipative evolution of a parametrically driven qubit-cavity system under the periodic modulation of coupling energy between two subsystems, which leads to the amplification of counter-rotating processes. We reveal a very rich dynamical behavior of this hybrid system. In particular, w...

[Phys. Rev. A 96, 043870] Published Mon Oct 30, 2017

Author(s): Valentin Link and Walter T. Strunz

We present a stochastic projection formalism for the description of quantum dynamics in bosonic or spin environments. The Schrödinger equation in the coherent state representation with respect to the environmental degrees of freedom can be reformulated by employing the Feshbach partitioning techniqu...

[Phys. Rev. Lett. 119, 180401] Published Mon Oct 30, 2017

Author(s): Daniel Carney, Laurent Chaurette, Dominik Neuenfeld, and Gordon Walter Semenoff

We discuss information-theoretic properties of low-energy photons and gravitons in the S matrix. Given an incoming n-particle momentum eigenstate, we demonstrate that unobserved soft photons decohere nearly all outgoing momentum superpositions of charged particles, while the universality of gravity ...

[Phys. Rev. Lett. 119, 180502] Published Mon Oct 30, 2017

Author(s): Dan Hooper

The latest results from two dark matter searches have further ruled out many theoretically attractive dark matter particle candidates.

[Physics 10, 119] Published Mon Oct 30, 2017

Categories: Physics

Author(s): Ashutosh Rai and Goutam Paul

Quantum entanglement has been recently demonstrated as a useful resource in conflicting-interest games of incomplete information between two players, Alice and Bob [Pappa *et al.*, Phys. Rev. Lett. **114**, 020401 (2015)]. The general setting for such games is that of correlated strategies where the corr...

[Phys. Rev. A 96, 042340] Published Mon Oct 30, 2017

Author(s): Fernando Nicacio, Andrea Valdés-Hernández, Ana P. Majtey, and Fabricio Toscano

Gaussian states are the backbone of quantum information protocols with continuous-variable systems whose power relies fundamentally on the entanglement between the different modes. In the case of global pure states, knowledge of the reduced states in a given bipartition of a multipartite quantum sys...

[Phys. Rev. A 96, 042341] Published Mon Oct 30, 2017