ABSTRACT
The one-dimensional, chiral edge channels of the quantum Hall effect are a promising platform in which to implement electron quantum optics experiments; however, Coulomb interactions between edge channels are a major source of decoherence and energy relaxation. It is therefore of large interest to understand the range and limitations of the simple quantum electron optics picture. Here we confirm experimentally for the first time the predicted relaxation and revival of electrons injected at finite energy into an edge channel. The observed decay of the injected electrons is reproduced theoretically within a Tomonaga-Luttinger liquid framework, including an important dissipation towards external degrees of freedom. This gives us a quantitative empirical understanding of the strength of the interaction and the dissipation.
ABSTRACT
We show experimentally that a dc biased Josephson junction in series with a high-enough-impedance microwave resonator emits antibunched photons. Our resonator is made of a simple microfabricated spiral coil that resonates at 4.4 GHz and reaches a 1.97 kΩ characteristic impedance. The second order correlation function of the power leaking out of the resonator drops down to 0.3 at zero delay, which demonstrates the antibunching of the photons emitted by the circuit at a rate of 6×10^{7} photons per second. Results are found in quantitative agreement with our theoretical predictions. This simple scheme could offer an efficient and bright single-photon source in the microwave domain.
ABSTRACT
This corrects the article DOI: 10.1103/PhysRevLett.114.126801.
ABSTRACT
We show that a properly dc-biased Josephson junction in series with two microwave resonators of different frequencies emits photon pairs in the resonators. By measuring auto- and intercorrelations of the power leaking out of the resonators, we demonstrate two-mode amplitude squeezing below the classical limit. This nonclassical microwave light emission is found to be in quantitative agreement with our theoretical predictions, up to an emission rate of 2 billion photon pairs per second.
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We derive fluctuation-dissipation relations for a tunnel junction driven through a resonator displaying strong quantum fluctuations. We find that the fluctuation-dissipation relations derived for classical external drives hold, provided the effect of the circuit's quantum fluctuations is incorporated into the modified nonlinear current voltage characteristics. We also demonstrate that all quantities measured under a time dependent bias can be reconstructed from their values measured under a dc bias using photoassisted tunneling relations. We confirm these predictions by implementing the circuit and measuring the dc current through the junction, its high frequency admittance, and its current noise at the frequency of the resonator.
ABSTRACT
The on-demand generation of pure quantum excitations is important for the operation of quantum systems, but it is particularly difficult for a system of fermions. This is because any perturbation affects all states below the Fermi energy, resulting in a complex superposition of particle and hole excitations. However, it was predicted nearly 20 years ago that a Lorentzian time-dependent potential with quantized flux generates a minimal excitation with only one particle and no hole. Here we report that such quasiparticles (hereafter termed levitons) can be generated on demand in a conductor by applying voltage pulses to a contact. Partitioning the excitations with an electronic beam splitter generates a current noise that we use to measure their number. Minimal-excitation states are observed for Lorentzian pulses, whereas for other pulse shapes there are significant contributions from holes. Further identification of levitons is provided in the energy domain with shot-noise spectroscopy, and in the time domain with electronic Hong-Ou-Mandel noise correlations. The latter, obtained by colliding synchronized levitons on a beam splitter, exemplifies the potential use of levitons for quantum information: using linear electron quantum optics in ballistic conductors, it is possible to imagine flying-qubit operation in which the Fermi statistics are exploited to entangle synchronized electrons emitted by distinct sources. Compared with electron sources based on quantum dots, the generation of levitons does not require delicate nanolithography, considerably simplifying the circuitry for scalability. Levitons are not limited to carrying a single charge, and so in a broader context n-particle levitons could find application in the study of full electron counting statistics. But they can also carry a fraction of charge if they are implemented in Luttinger liquids or in fractional quantum Hall edge channels; this allows the study of Abelian and non-Abelian quasiparticles in the time domain. Finally, the generation technique could be applied to cold atomic gases, leading to the possibility of atomic levitons.
ABSTRACT
We investigate electron dynamics at the graphene edge by studying the propagation of collective edge magnetoplasmon excitations. By timing the travel of narrow wave packets on picosecond time scales around exfoliated samples, we find chiral propagation with low attenuation at a velocity that is quantized on Hall plateaus. We extract the carrier drift contribution from the edge magnetoplasmon propagation and find it to be slightly less than the Fermi velocity, as expected for an abrupt edge. We also extract the characteristic length for Coulomb interaction at the edge and find it to be smaller than that for soft depletion-edge systems.
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We present an experiment where the quantum coherence in the edge states of the integer quantum Hall regime is tuned with a decoupling gate. The coherence length is determined by measuring the visibility of quantum interferences in a Mach-Zehnder interferometer as a function of temperature, in the quantum Hall regime at a filling factor 2. The temperature dependence of the coherence length can be varied by a factor of 2. The strengthening of the phase coherence at finite temperature is shown to arise from a reduction of the coupling between copropagating edge states. This opens the way for a strong improvement of the phase coherence of quantum Hall systems. The decoupling gate also allows us to investigate how interedge state coupling influences the quantum interferences' dependence on the injection bias. We find that the finite bias visibility can be decomposed into two contributions: a Gaussian envelope which is surprisingly insensitive to the coupling, and a beating component which, on the contrary, is strongly affected by the coupling.
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A cross-sectional study involving 143 farrow-to-finish herds was carried out to identify herd-level noninfectious factors associated with pneumonia and pleuritis in slaughter pigs. Data related to herd characteristics, biosecurity, management and housing conditions were collected by questionnaire during a farm visit. Climatic conditions were measured over 20 h in the post-weaning and finishing rooms where the slaughter pigs were kept. After these on-farm investigations, the finishing pigs were examined at slaughter for lung lesions. A sample of 30 randomly selected pigs per herd was scored for pneumonia and pleuritis. Herds were grouped into three categories according to their pneumonia median score (class 1: ≤ 0.5; class 2: 0.5
Subject(s)
Pleurisy/veterinary , Pneumonia/veterinary , Swine Diseases/epidemiology , Abattoirs , Animal Husbandry , Animals , Cross-Sectional Studies , France/epidemiology , Humans , Logistic Models , Lung/pathology , Pleurisy/epidemiology , Pneumonia/epidemiology , Risk Factors , Surveys and Questionnaires , Swine , Swine Diseases/pathologyABSTRACT
We explore the photonic (bright) side of the dynamical Coulomb blockade (DCB) by measuring the radiation emitted by a dc voltage-biased Josephson junction embedded in a microwave resonator. In this regime Cooper pair tunneling is inelastic and associated with the transfer of an energy 2eV into the resonator modes. We have measured simultaneously the Cooper pair current and the photon emission rate at the resonance frequency of the resonator. Our results show two regimes, in which each tunneling Cooper pair emits either one or two photons into the resonator. The spectral properties of the emitted radiation are accounted for by an extension to DCB theory.
Subject(s)
Continuous Positive Airway Pressure/methods , Sleep Apnea, Obstructive/therapy , Ambulatory Care , Continuous Positive Airway Pressure/instrumentation , Follow-Up Studies , Heart Failure/complications , Humans , Hypertension/complications , Masks , Myocardial Ischemia/complications , Sleep Apnea, Obstructive/classification , Time Factors , Treatment OutcomeABSTRACT
We report on an Hanbury Brown-Twiss experiment probing the statistics of microwave photons emitted by a tunnel junction in the shot-noise regime at low temperature. By measuring the cross correlation of the fluctuations of the occupation numbers of the photon modes of both detection branches, we show that while the statistics of electrons is Poissonian, the photons obey chaotic statistics. This is observed even for low photon occupation number when the voltage across the junction is close to hν/e.
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We report on conductance measurements in carbon nanotube based double quantum dots connected to two normal electrodes and a central superconducting finger. By operating our devices as beam splitters, we provide evidence for crossed Andreev reflections tunable in situ. This opens an avenue to more sophisticated quantum opticslike experiments with spin entangled electrons.
ABSTRACT
We present an experiment where we tune the decoherence in a quantum interferometer using one of the simplest objects available in the physics of quantum conductors: an Ohmic contact. For that purpose, we designed an electronic Mach-Zehnder interferometer which has one of its two arms connected to an Ohmic contact through a quantum point contact. At low temperature, we observe quantum interference patterns with a visibility up to 57%. Increasing the connection between one arm of the interferometer to the floating Ohmic contact, the voltage probe, reduces quantum interference as it probes the electron trajectory. This unique experimental realization of a voltage probe works as a trivial which-path detector whose efficiency can be simply tuned by a gate voltage.
Subject(s)
Chest Pain/etiology , Kidney Diseases/diagnosis , Lung Diseases/diagnosis , Malacoplakia/diagnosis , Aged , Anti-Bacterial Agents/therapeutic use , Drainage , Escherichia coli Infections/diagnosis , Escherichia coli Infections/drug therapy , Female , Humans , Kidney Diseases/surgery , Lung Diseases/therapy , Malacoplakia/therapyABSTRACT
An electronic Mach-Zehnder interferometer is used in the integer quantum Hall regime at a filling factor 2 to study the dephasing of the interferences. This is found to be induced by the electrical noise existing in the edge states capacitively coupled to each other. Electrical shot noise created in one channel leads to phase randomization in the other, which destroys the interference pattern. These findings are extended to the dephasing induced by thermal noise instead of shot noise: it explains the underlying mechanism responsible for the finite temperature coherence time tau_{phi}(T) of the edge states at filling factor 2, measured in a recent experiment. Finally, we present here a theory of the dephasing based on Gaussian noise, which is found to be in excellent agreement with our experimental results.
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We have determined the finite temperature coherence length of edge states in the integer quantum Hall effect regime. This was realized by measuring the visibility of electronic Mach-Zehnder interferometers of different sizes, at filling factor 2. The visibility shows an exponential decay with the temperature. The characteristic temperature scale is found inversely proportional to the length of the interferometer arm, allowing one to define a coherence length l_(phi). The variations of l_(phi) with magnetic field are the same for all samples, with a maximum located at the upper end of the quantum Hall plateau. Our results provide the first accurate determination of l_(phi) in the quantum Hall regime.
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OBJECTIVES: Otitis media with effusion are defined as the persistence of middle ear effusion for more than 3 weeks. If the diagnostic is easy, questions remain about pathogeny and treatment. MATERIALS AND METHODS: Literature was reviewed regarding the pathogeny and the best treatment strategy. RESULTS: Except in the case of middle ear effusion due to trauma, effusion is an exudate due to mucous cell metaplasia. The main causal factor is middle ear inflammation, which is secondary to viral or bacterial infection. Inflammation causes dysfunction of the sodium transports in the middle ear. Responsibility of the otitis media with effusion in the genesis of the various chronic otitis media remains controversial. Treatment is justified when otitis media last more than 3 months, that is to say few months observation is required. The aim of treatment is to reduce local inflammation and to treat effusion. Prevention and treatment of local inflammation is difficult. Indeed, it is difficult to avoid rhinitis that is mainly viral. Effusion must be treated in order to avoid local middle ear deterioration and language deficiency. Insertion of tympanostomy tube is the only effective treatment. It decreases middle ear depression and Eustachian tube obstruction and restores the mucociliary clearance. Adenoidectomy and amygdalectomy are not effective in otitis media with effusion but, in association with tympanostomy tube, could decrease recurrence of acute otitis media. CONCLUSION: Otitis media with effusion remains a frequent disorder, for which the only effective treatment is the tympanostomy tube.
Subject(s)
Otitis Media with Effusion/microbiology , Anti-Infective Agents/therapeutic use , Cerebrospinal Fluid Otorrhea/etiology , Humans , Otitis Media with Effusion/complications , Otitis Media with Effusion/therapy , Otologic Surgical ProceduresABSTRACT
BACKGROUND AND PURPOSE: Compliance with continuous positive airway pressure (CPAP) treatment in obstructive sleep apnoea syndrome (OSAS) may be difficult. Patient education is important but strategies and their outcomes are not clear. PATIENTS AND METHODS: We studied the effects of four education strategies on compliance and quality of life changes with CPAP treatment in seven centres in the French ANTADIR homecare network. Patients received from prescribers either a simple oral explanation (SP) or an oral and written explanation (RP) of CPAP use. In addition, they received from homecare technicians either a single home visit (SH) at CPAP onset or repeated home visits at CPAP onset and at 1 week, 1 month and 3 months after (RH). Compliance and quality of life were evaluated at CPAP onset, and at 3, 6 and 12 months after initiation of treatment. RESULTS: One hundred twelve patients with severe OSAS (mean age 58+/-11 year, apnoea-hypopnoea index 58+/-25/h) were allocated randomly to groups (SP+SH; SP+RH; RP+SH; RP+RH) with no initial differences. Quality of life, evaluated by the generic SF-36 questionnaire, improved in the combined emotional domains. Compliance was over 5h in all four education groups. These effects were sustained over 12 months and were not different between the four groups. We conclude that standard education strategies for CPAP induction in France are sufficient for good compliance and improved quality of life with CPAP. Education with reinforced input should be focussed on identified subgroups prone to problems.
Subject(s)
Continuous Positive Airway Pressure/methods , Patient Education as Topic , Sleep Apnea, Obstructive/diagnosis , Sleep Apnea, Obstructive/therapy , Affect , Female , Follow-Up Studies , Home Care Services , Humans , Male , Middle Aged , Quality of Life/psychology , Severity of Illness Index , Surveys and QuestionnairesABSTRACT
We report on direct measurements of the electronic shot noise of a quantum point contact at frequencies nu in the range 4-8 GHz. The very small energy scale used ensures energy independent transmissions of the few transmitted electronic modes and their accurate knowledge. Both the thermal energy and the quantum point contact drain-source voltage V_{ds} are comparable to the photon energy hnu leading to observation of the shot noise suppression when V_{ds}