Physical Review Letters

Gammelmark, Søren; Julsgaard, Brian; Mølmer, Klaus

doi: 10.1103/PhysRevLett.111.160401pmid: 24182235

A density matrix ρ ( t ) yields probabilistic information about the outcome of measurements on a quantum system. We introduce here the past quantum state, which, at time T , accounts for the state of a quantum system at earlier times t < T . The past quantum state Ξ ( t ) is composed of two objects, ρ ( t ) and E ( t ) , conditioned on the dynamics and the probing of the system until t and in the time interval ( t , T ), respectively. The past quantum state is characterized by its ability to make better predictions for the unknown outcome of any measurement at t than the conventional quantum state at that time. On the one hand, our formalism shows how smoothing procedures for estimation of past classical signals by a quantum probe (M. Tsang, Phys. Rev. Lett. 102 , 250403 ( 2009 ) PRLTAO 0031-9007 10.1103/PhysRevLett.102.250403 ) apply also to describe the past state of the quantum system itself. On the other hand, it generalizes theories of pre- and postselected quantum states (Y. Aharonov and L. Vaidman, J. Phys. A 24 , 2315 ( 1991 ) JPHAC5 0305-4470 10.1088/0305-4470/24/10/018 ) to systems subject to any quantum measurement scenario, any coherent evolution, and any Markovian dissipation processes.

Sindona, A.; Goold, J.; Lo Gullo, N.; Lorenzo, S.; Plastina, F.

doi: 10.1103/PhysRevLett.111.165303pmid: 24182277

The Fermi-edge singularity and the Anderson orthogonality catastrophe describe the universal physics which occurs when a Fermi sea is locally quenched by the sudden switching of a scattering potential, leading to a brutal disturbance of its ground state. We demonstrate that the effect can be seen in the controllable domain of ultracold trapped gases by providing an analytic description of the out-<?format ?>of-equilibrium response to an atomic impurity, both at zero and at finite temperature. Furthermore, we link the transient behavior of the gas to the decoherence of the impurity, and to the degree of the non-Markovian nature of its dynamics.

Kravec, S.; McGreevy, John

doi: 10.1103/PhysRevLett.111.161603pmid: 24182254

It is possible to characterize certain states of matter by properties of their edge states. This implies a notion of “surface-only models”: models which can only be regularized at the edge of a higher-dimensional system. After incorporating the fermion-doubling results of Nielsen and Ninomiya into this framework, we employ this idea to identify new obstructions to symmetry-preserving regulators of quantum field theory. We focus on an example which forbids regulated models of Maxwell theory with manifest electromagnetic duality symmetry.

Kim, I Jong; Pae, Ki Hong; Kim, Chul Min; Kim, Hyung Taek; Sung, Jae Hee; Lee, Seong Ku; Yu, Tae Jun; Choi, Il Woo; Lee, Chang-Lyoul Woo; Nam, Kee Hwan; Nickles, Peter V; Jeong, Tae Moon; Lee, Jongmin Moon

Kennedy, Tom

doi: 10.1103/PhysRevLett.111.165703pmid: 24182282

We show that if the three-dimensional self-avoiding walk (SAW) is conformally invariant, then one can compute the hitting densities for the SAW in a half-space and in a sphere. We test these predictions by Monte Carlo simulations and find excellent agreement, thus providing evidence that the SAW is conformally invariant in three dimensions.

Sumetsky, M

doi: 10.1103/PhysRevLett.111.163901pmid: 24182267

It is shown theoretically that an optical bottle resonator with a nanoscale radius variation can perform a multinanosecond long dispersionless delay of light in a nanometer-order bandwidth with minimal losses. Experimentally, a 3 mm long resonator with a 2.8 nm deep semiparabolic radius variation is fabricated from a 19 μ m radius silica fiber with a subangstrom precision. In excellent agreement with theory, the resonator exhibits the impedance-matched 2.58 ns (3 bytes) delay of 100 ps pulses with 0.44 dB / ns intrinsic loss. This is a miniature slow light delay line with the record large delay time, record small transmission loss, dispersion, and effective speed of light.

Alarcon, R; Balascuta, S; Benson, S. V; Bertozzi, W. V; Boyce, J. R; Cowan, R. R; Douglas, D. R; Evtushenko, P. R; Fisher, P. R; Ihloff, E. R; Kalantarians, N. R; Kelleher, A. R; Legg, R. R; Milner, R. G; Neil, G. R; Ou, L. R;

Mattioli, Marco ; Dalmonte, Marcello ; Lechner, Wolfgang ; Pupillo, Guido

doi: 10.1103/PhysRevLett.111.165302pmid: 24182276

We investigate the zero-temperature phases of bosonic and fermionic gases confined to one dimension and interacting via a class of finite-range soft-shoulder potentials (i.e., soft-core potentials with an additional hard-core onsite interaction). Using a combination of analytical and numerical methods, we demonstrate the stabilization of critical quantum liquids with qualitatively new features with respect to <?format ?>the Tomonaga-Luttinger liquid paradigm. These features result from frustration and cluster formation in the corresponding classical ground state. Characteristic signatures of these liquids are accessible in state-of-the-art experimental setups with Rydberg-dressed ground-state atoms trapped in optical lattices.

Kling, Nora G; Betsch, K. J; Zohrabi, M. J; Zeng, S. J; Anis, F. J; Ablikim, U. J; Jochim, Bethany J; Wang, Z. J; Kübel, M. J; Kling, M. F; Carnes, K. D; Esry, B. D; Ben-Itzhak, I. D

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Peruzzo, Paolo ; Defina, Andrea ; Nepf, Heidi M; Stocker, Roman M

doi: 10.1103/PhysRevLett.111.164501pmid: 24182270

Surface-piercing vegetation often captures particles that flow on the water surface, where surface tension forces contribute to capture. Yet the physics of capillary capture in flow has not been addressed. Here we model the capture of floating particles by surface-piercing collectors at moderately low Reynolds numbers ( Re < 10 ). We find a trade-off between the capillary force, which increases with the collector diameter, and the relative size of the meniscus, which decreases with the collector diameter, resulting in an optimal collector diameter of ∼ 1 - 10 mm that corresponds to the regime in which many aquatic plant species operate. For this diameter range the angular distribution of capture events is nearly uniform and capture can be orders of magnitude more efficient than direct interception, showing that capillary forces can be major contributors to the capture of seeds and particulate matter by organisms.