35 research outputs found
Landauer's erasure principle in a squeezed thermal memory
Landauer's erasure principle states that the irreversible erasure of a
one-bit memory, embedded in a thermal environment, is accompanied with a work
input of at least . Fundamental to that principle is the
assumption that the physical states representing the two possible logical
states are close to thermal equilibrium. Here, we propose and theoretically
analyze a minimalist mechanical model of a one-bit memory operating with
squeezed thermal states. It is shown that the Landauer energy bound is
exponentially lowered with increasing squeezing factor. Squeezed thermal
states, which may naturally arise in digital electronic circuits operating in a
pulse-driven fashion, thus can be exploited to reduce the fundamental energy
costs of an erasure operation.Comment: 5 pages, 3 figure
Squeezed thermal reservoirs as a resource for a nano-mechanical engine beyond the Carnot limit
The efficient conversion of thermal energy to mechanical work by a heat
engine is an ongoing technological challenge. Since the pioneering work of
Carnot, it is known that the efficiency of heat engines is bounded by a
fundamental upper limit, the Carnot limit. Theoretical studies suggest that
heat engines may be operated beyond the Carnot limit by exploiting stationary,
non-equilibrium reservoirs that are characterized by a temperature as well as
further parameters. In a proof-of-principle experiment, we demonstrate that the
efficiency of a nano-beam heat engine coupled to squeezed thermal noise is not
bounded by the standard Carnot limit. Remarkably, we also show that it is
possible to design a cyclic process that allows for extraction of mechanical
work from a single squeezed thermal reservoir. Our results demonstrate a
qualitatively new regime of non-equilibrium thermodynamics at small scales and
provide a new perspective on the design of efficient, highly miniaturized
engines.Comment: 5 pages, 3 figure
Bose-Einstein Condensation of Photons versus Lasing and Hanbury Brown-Twiss Measurements with a Condensate of Light
The advent of controlled experimental accessibility of Bose-Einstein
condensates, as realized with e.g. cold atomic gases, exciton-polaritons, and
more recently photons in a dye-filled optical microcavity, has paved the way
for new studies and tests of a plethora of fundamental concepts in quantum
physics. We here describe recent experiments studying a transition between
laser-like dynamics and Bose-Einstein condensation of photons in the dye
microcavity system. Further, measurements of the second-order coherence of the
photon condensate are presented. In the condensed state we observe photon
number fluctuations of order of the total particle number, as understood from
effective particle exchange with the photo-excitable dye molecules. The
observed intensity fluctuation properties give evidence for Bose-Einstein
condensation occurring in the grand-canonical statistical ensemble regime
Particle motion associated with wave function density gradients
We study the quantum mechanical motion of massive particles in a system of
two coupled waveguide potentials, where the population transfer between the
waveguides effectively acts as a clock and allows particle velocities to be
determined. Application of this scheme to evanescent phenomena at a reflective
step potential reveals an energy-velocity relationship for classically
forbidden motion. Regions of gain and loss, as described by imaginary
potentials, are shown to speed up the motion of particles. We argue that phase
and density gradients in quantum mechanical wave functions play complementary
roles in indicating the speed of particles.Comment: 6 pages, 4 figure