40 research outputs found
Bending the rules: Quantum effects in the operation of a microscopic heat engine in diamond
No full textA classical heat engine that extracts work from thermal sources and which does not include coherence amongst its microscopic degrees of freedom is a fundamental concept of classical thermodynamics. In contrast, the internal states of a quantum heat engine (QHE) can exist in a coherent superposition of energy levels and a question of interest for such a QHE is whether it can exhibit thermodynamic behavior fundamentally different to that allowed in a classical engine. QHEs have recently been implemented using for example trapped ions [1]. However, experiments so far have not shown any non-classical features in their thermodynamic quantities. While the efficiency of a QHE is still bound by the Carnot limit, recent theoretical predictions show that coherence can boost its power output above the classically allowed limit for an engine using the same thermal resources [2]. Moreover, the presence of coherence was predicted to result in the equivalence of different QHE types in the limit of weak driving and short cycle duration.</p
Ultrahigh and persistent optical depths of cesium in Kagomé-type hollow-core photonic crystal fibers
No full textAlkali-filled hollow-core fibers are a promising medium for investigating light–matter interactions, especially at the single-photon level, due to the tight confinement of light and high optical depths achievable by light-induced atomic desorption (LIAD). However, until now these large optical depths could only be generated for seconds, at most once per day, severely limiting the practicality of the technology. Here we report the generation of the highest observed transient (>105 for up to a minute) and highest observed persistent (>2000 for hours) optical depths of alkali vapors in a light-guiding geometry to date, using a cesium-filled Kagomé-type hollow-core photonic crystal fiber (HC-PCF). Our results pave the way to light–matter interaction experiments in confined geometries requiring long operation times and large atomic number densities, such as generation of single-photon-level nonlinearities and development of single photon quantum memories
Experimental demonstration of quantum effects in the operation of microscopic heat engines
No full textThe ability of the internal states of a working fluid to be in a coherent superposition is one of the basic properties of a quantum heat engine. It was recently predicted that in the regime of small engine action, this ability can enable a quantum heat engine to produce more power than any equivalent classical heat engine. It was also predicted that in the same regime, the presence of such internal coherence causes different types of quantum heat engines to become thermodynamically equivalent. Here, we use an ensemble of nitrogen vacancy centers in diamond for implementing two types of quantum heat engines, and experimentally observe both effects
Fast, noise-free atomic optical memory with 35% end-to-end efficiency
No full textCoherent optical memories will likely play an important role in future
quantum communication networks. Among the different platforms, memories based
on ladder-type orbital transitions in atomic gasses offer high bandwidth
( MHz), continuous (on-demand) readout, and low-noise operation. Here we
report on an upgraded setup of our previously-reported fast ladder memory, with
improved efficiency and lifetime, and reduced noise. The upgrade employs a
stronger control field, wider signal beam, reduced atomic density, higher
optical depth, annular optical-pumping beam, and weak dressing of an auxiliary
orbital to counteract residual Doppler-broadening. For a 2 ns-long pulse, we
demonstrate 53% internal efficiency, 35% end-to-end efficiency, noise photons per pulse, and a lifetime of 108 ns. This
combination of performances is a record for continuous-readout memories
Fast, noise-free memory for photon synchronization at room temperature
No full textWe implement a new, noise-free, broadband light storage scheme, opening the way to faithful multiphoton synchronization.</jats:p
Single-photon synchronization with a room-temperature atomic quantum memory
No full textEfficient synchronization of single photons that are compatible with
narrowband atomic transitions is an outstanding challenge, which could prove
essential for photonic quantum information processing. Here we report on the
synchronization of independently-generated single photons using a
room-temperature atomic quantum memory. The photon source and the memory are
interconnected by fibers and employ the same ladder-level atomic scheme. We
store and retrieve the heralded single photons with end-to-end efficiency of
and final anti-bunching of . Our
synchronization process results in over tenfold increase in the photon-pair
coincidence rate, reaching a rate of more than detected synchronized
photon pairs per second. The indistinguishability of the synchronized photons
is verified by a Hong-Ou-Mandel interference measurement
