scholarly journals Quantum variance: A measure of quantum coherence and quantum correlations for many-body systems

2016 ◽  
Vol 94 (7) ◽  
Author(s):  
Irénée Frérot ◽  
Tommaso Roscilde
Keyword(s):  
Quantum Coherence ◽  
Quantum Correlations ◽  
Many Body ◽  
Many Body Systems ◽  
Quantum Variance

scholarly journals Universal relations for ultracold reactive molecules

2020 ◽  
Vol 6 (51) ◽  
pp. eabd4699
Author(s):  
Mingyuan He ◽  
Chenwei Lv ◽  
Hai-Qing Lin ◽  
Qi Zhou
Keyword(s):  
Critical Role ◽  
Interaction Strength ◽  
Quantum Correlations ◽  
Polar Molecules ◽  
Many Body ◽  
Density Correlation ◽  
Ultracold Polar Molecules ◽  
Unexplored Area ◽  
Many Body Systems

The realization of ultracold polar molecules in laboratories has pushed physics and chemistry to new realms. In particular, these polar molecules offer scientists unprecedented opportunities to explore chemical reactions in the ultracold regime where quantum effects become profound. However, a key question about how two-body losses depend on quantum correlations in interacting many-body systems remains open so far. Here, we present a number of universal relations that directly connect two-body losses to other physical observables, including the momentum distribution and density correlation functions. These relations, which are valid for arbitrary microscopic parameters, such as the particle number, the temperature, and the interaction strength, unfold the critical role of contacts, a fundamental quantity of dilute quantum systems, in determining the reaction rate of quantum reactive molecules in a many-body environment. Our work opens the door to an unexplored area intertwining quantum chemistry; atomic, molecular, and optical physics; and condensed matter physics.

scholarly journals Coherent spin manipulation of individual atoms on a surface

Science ◽  
2019 ◽  
Vol 366 (6464) ◽  
pp. 509-512 ◽  
Author(s):  
Kai Yang ◽  
William Paul ◽  
Soo-Hyon Phark ◽  
Philip Willke ◽  
Yujeong Bae ◽  
...  
Keyword(s):  
Quantum Coherence ◽  
Coherent Control ◽  
Spin Echo ◽  
Magnetic Interaction ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Many Body ◽  
Many Body Systems ◽  
Coherent Spin

Achieving time-domain control of quantum states with atomic-scale spatial resolution in nanostructures is a long-term goal in quantum nanoscience and spintronics. Here, we demonstrate coherent spin rotations of individual atoms on a surface at the nanosecond time scale, using an all-electric scheme in a scanning tunneling microscope (STM). By modulating the atomically confined magnetic interaction between the STM tip and surface atoms, we drive quantum Rabi oscillations between spin-up and spin-down states in as little as ~20 nanoseconds. Ramsey fringes and spin echo signals allow us to understand and improve quantum coherence. We further demonstrate coherent operations on engineered atomic dimers. The coherent control of spins arranged with atomic precision provides a solid-state platform for quantum-state engineering and simulation of many-body systems.

scholarly journals Novel quantum phase transition from bounded to extensive entanglement

2017 ◽  
Vol 114 (20) ◽  
pp. 5142-5146 ◽  
Author(s):  
Zhao Zhang ◽  
Amr Ahmadain ◽  
Israel Klich
Keyword(s):  
Phase Transition ◽  
Quantum Phase Transition ◽  
Ground States ◽  
Quantum Correlations ◽  
Quantum Phase ◽  
Continuous Family ◽  
Many Body ◽  
Many Body Systems ◽  
Special Circumstances ◽  
Area Law

The nature of entanglement in many-body systems is a focus of intense research with the observation that entanglement holds interesting information about quantum correlations in large systems and their relation to phase transitions. In particular, it is well known that although generic, many-body states have large, extensive entropy, ground states of reasonable local Hamiltonians carry much smaller entropy, often associated with the boundary length through the so-called area law. Here we introduce a continuous family of frustration-free Hamiltonians with exactly solvable ground states and uncover a remarkable quantum phase transition whereby the entanglement scaling changes from area law into extensively large entropy. This transition shows that entanglement in many-body systems may be enhanced under special circumstances with a potential for generating “useful” entanglement for the purpose of quantum computing and that the full implications of locality and its restrictions on possible ground states may hold further surprises.

scholarly journals GLOBAL QUANTUM CORRELATIONS IN THE ISING MODEL

2011 ◽  
Vol 09 (07n08) ◽  
pp. 1685-1699 ◽  
Author(s):  
STEVE CAMPBELL ◽  
LAURA MAZZOLA ◽  
MAURO PATERNOSTRO
Keyword(s):  
Magnetic Field ◽  
Ising Model ◽  
Figure Of Merit ◽  
Quantum Correlations ◽  
Transverse Magnetic ◽  
Many Body ◽  
Standard Quantum ◽  
Global Properties ◽  
Spin Quantum ◽  
Many Body Systems

We study quantum correlations in an isotropic Ising ring under the effects of a transverse magnetic field. After characterizing the behavior of two-spin quantum correlations, we extend our analysis to global properties of the ring, using a figure of merit for quantum correlations that shows enough sensitivity to reveal the drastic changes in the properties of the system at criticality. This opens up the possibility to relate statistical properties of quantum many-body systems to suitably tailored measures of quantum correlations that capture features going far beyond standard quantum entanglement.

REGULAR STRUCTURE OF LOW-LYING STATES FOR ATOMIC NUCLEI UNDER RANDOM INTERACTIONS

2008 ◽  
Vol 17 (supp01) ◽  
pp. 304-317
Author(s):  
Y. M. ZHAO
Keyword(s):  
Ground State ◽  
Collective Motion ◽  
Regular Structure ◽  
Positive Parity ◽  
Many Body ◽  
Random Interactions ◽  
Atomic Nuclei ◽  
Many Body Systems

In this paper we review regularities of low-lying states for many-body systems, in particular, atomic nuclei, under random interactions. We shall discuss the famous problem of spin zero ground state dominance, positive parity dominance, collective motion, odd-even staggering, average energies, etc., in the presence of random interactions.

scholarly journals Emergence of a Renormalized 1/N Expansion in Quenched Critical Many-Body Systems

2021 ◽  
Vol 126 (11) ◽  
Author(s):  
Benjamin Geiger ◽  
Juan Diego Urbina ◽  
Klaus Richter
Keyword(s):  
Many Body ◽  
Many Body Systems

scholarly journals Continuous Phase Transition without Gap Closing in Non-Hermitian Quantum Many-Body Systems

2020 ◽  
Vol 125 (26) ◽  
Author(s):  
Norifumi Matsumoto ◽  
Kohei Kawabata ◽  
Yuto Ashida ◽  
Shunsuke Furukawa ◽  
Masahito Ueda
Keyword(s):  
Phase Transition ◽  
Continuous Phase ◽  
Many Body ◽  
Continuous Phase Transition ◽  
Many Body Systems ◽  
Gap Closing
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