393 research outputs found
Quantum and classical dynamics of a three-mode absorption refrigerator
We study the quantum and classical evolution of a system of three harmonic
modes interacting via a trilinear Hamiltonian. With the modes prepared in
thermal states of different temperatures, this model describes the working
principle of an absorption refrigerator that transfers energy from a cold to a
hot environment at the expense of free energy provided by a high-temperature
work reservoir. Inspired by a recent experimental realization with trapped
ions, we elucidate key features of the coupling Hamiltonian that are relevant
for the refrigerator performance. The coherent system dynamics exhibits rapid
effective equilibration of the mode energies and correlations, as well as a
transient enhancement of the cooling performance at short times. We find that
these features can be fully reproduced in a classical framework.Comment: 11 pages, 8 figures; additions and corrections; accepted in Quantum
on 2017-12-0
EXPERIMENTAL ENTANGLEMENT WITNESS FAMILY MEASUREMENT AND THEORETICAL ASPECTS OF QUANTUM TOMOGRAPHY
Ph.DDOCTOR OF PHILOSOPH
Past of a quantum particle: Common sense prevails
We analyze Vaidman's three-path interferometer with weak path marking [Phys.
Rev. A 87, 052104 (2013)] and find that common sense yields correct statements
about the particle's path through the interferometer. This disagrees with the
original claim that the particles have discontinuous trajectories at odds with
common sense. In our analysis, "the particle's path" has operational meaning as
acquired by a path-discriminating measurement. For a quantum-mechanical
experimental demonstration of the case, one should perform a single-photon
version of the experiment by Danan et al. [Phys. Rev. Lett. 111, 240402 (2013)]
with unambiguous path discrimination. We present a detailed proposal for such
an experiment.Comment: v1: 20 pages, 15 figures; v2 and v3: 20 pages, 16 figures, text and
figures edited, references update
Quantum absorption refrigerator with trapped ions
Thermodynamics is one of the oldest and well-established branches of physics
that sets boundaries to what can possibly be achieved in macroscopic systems.
While it started as a purely classical theory, it was realized in the early
days of quantum mechanics that large quantum devices, such as masers or lasers,
can be treated with the thermodynamic formalism. Remarkable progress has been
made recently in the miniaturization of heat engines all the way to the single
Brownian particle as well as to a single atom. However, despite several
theoretical proposals, the implementation of heat machines in the fully quantum
regime remains a challenge. Here, we report an experimental realization of a
quantum absorption refrigerator in a system of three trapped ions, with three
of its normal modes of motion coupled by a trilinear Hamiltonian such that heat
transfer between two modes refrigerates the third. We investigate the dynamics
and steady-state properties of the refrigerator and compare its cooling
capability when only thermal states are involved to the case when squeezing is
employed as a quantum resource. We also study the performance of such a
refrigerator in the single shot regime, and demonstrate cooling below both the
steady-state energy and the benchmark predicted by the classical thermodynamics
treatment.Comment: 11 pages, 7 figures, 2 table
Multidifferential study of identified charged hadron distributions in -tagged jets in proton-proton collisions at 13 TeV
Jet fragmentation functions are measured for the first time in proton-proton
collisions for charged pions, kaons, and protons within jets recoiling against
a boson. The charged-hadron distributions are studied longitudinally and
transversely to the jet direction for jets with transverse momentum 20 GeV and in the pseudorapidity range . The
data sample was collected with the LHCb experiment at a center-of-mass energy
of 13 TeV, corresponding to an integrated luminosity of 1.64 fb. Triple
differential distributions as a function of the hadron longitudinal momentum
fraction, hadron transverse momentum, and jet transverse momentum are also
measured for the first time. This helps constrain transverse-momentum-dependent
fragmentation functions. Differences in the shapes and magnitudes of the
measured distributions for the different hadron species provide insights into
the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb
public pages
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