We report the experimental realization of a single-atom heat engine. An ion is confined in a linear Paul trap with tapered geometry and driven thermally by coupling it alternately to hot and cold reservoirs. The output power of the engine is used to drive a harmonic oscillation. From direct measurements of the ion dynamics, we determine the thermodynamic cycles for various temperature differences of the reservoirs. We use these cycles to evaluate power P and efficiency η of the engine, obtaining up to P = 342 yJ and η = 2.8 , consistent with analytical estimations. Our results demonstrate that thermal machines can be reduced to the ultimate limit of single atoms.Heat engines have played a central role in our modern society since the industrial revolution. Converting thermal energy into mechanical work, they are ubiquitously employed to generate motion, from cars to airplanes [1]. The working fluid of a macroscopic engine typically contains of the order of 10 24 particles. In the last decade, dramatic experimental progress has lead to the miniaturization of thermal machines down to the microscale, using microelectromechanical [2], piezoresistive [3] and cold atom [4] systems, as well as single colloidal particles [5,6] and single molecules [7]. In his 1959 talk "There is plenty of room at the bottom", Richard Feynman already envisioned tiny motors working at the atomic level [8]. However, to date no such device has been built.Here we report the realization of a single-atom heat engine whose working agent is an ion, held within a modified linear Paul trap. We use laser cooling and electric field noise to engineer cold and hot reservoirs. We further employ fast thermometry methods to determine the temperature of the ion [9]. The thermodynamic cycle of the engine is established for various temperature differences of the reservoirs, from which we deduce work and heat, and thus power output and efficiency. We additionally show that the work produced by the engine can be effectively stored and used to drive an oscillator against friction. Our device demonstrates the working principles of a thermodynamic heat engine with a working agent reduced to the ultimate single particle limit, thus fulfilling Feynman's dream.Trapped ions offer an exceptional degree of preparation, control and measurement of their parameters, allowing for ground state cooling [10] and coupling to engineered reservoirs [11]. Owing to their unique properties, they have recently become invaluable tools for the investigation of quantum thermodynamics [12][13][14][15][16][17]. They additionally provide an ideal setup to operate and characterize a single particle heat engine.In our experiment, a single 40 Ca + ion is trapped in a linear Paul trap with a funnel-shaped electrode geometry, as shown in Fig. 1a [15]. The electrodes are driven symmetrically at a radio-frequency voltage of 830 V pp at 21 MHz, resulting in a tapered harmonic pseudopotential [10] of the form U = (m/2) i ω 2 i i 2 , where m is the atomic mass and i ∈ {x, y} denote the trap axes as...
Photon blockade is a dynamical quantum-nonlinear effect in driven systems with an anharmonic energy ladder. For a single atom strongly coupled to an optical cavity, we show that atom driving gives a decisively larger optical nonlinearity than cavity driving. This enhances single-photon blockade and allows for the implementation of two-photon blockade where the absorption of two photons suppresses the absorption of further photons. As a signature, we report on three-photon antibunching with simultaneous two-photon bunching observed in the light emitted from the cavity. Our experiment constitutes a significant step towards multiphoton quantum-nonlinear optics.
We experimentally demonstrate a method to determine the temperature of trapped ions which is suitable for monitoring fast thermalization processes. We show that observing and analyzing the lineshape of dark resonances in the fluorescence spectrum provides a temperature measurement which is accurate over a large dynamic range, applied to single ions and small ion crystals. Laser induced fluorescence is detected over a time of only μ 20 s, allowing for rapid determination of the ion temperature. In the measurement range of 10 −1 -10 2 mK we reach better than 15% accuracy. Tuning the cooling laser to selected resonance features allows us to control the ion temperatures between 0.7 mK and more than 10 mK. Experimental work is supported by a solution of the eight-level optical Bloch equations when including the ions' classical motion. This technique paves the way for many experiments, including heat transport in ion strings, heat engines, non-equilibrium thermodynamics or thermometry of large ion crystals.
We show an optical wave-mixing scheme that generates quantum light by means of a single three-level atom. The atom couples to an optical cavity and two laser fields that together drive a cycling current within the atom. Weak driving in combination with strong atom-cavity coupling induces transitions between the dark states of the system, accompanied by single-photon emission and suppression of atomic excitation by quantum interference. For strong driving, the system can generate coherent or Schrödinger cat-like fields with frequencies distinct from those of the applied lasers.Many scientific and technological advances during the last decades, across diverse areas of human knowledge, can be associated to the manipulation of light-matter interaction and the generation of light fields in particular. One such achievement is the laser [1]. Here a photon stimulates an atom to decay into the ground state at the expense of the emission of another photon. To amplify this process, the emitting medium (atoms) is placed inside an optical resonator where the repeated reflection of the light allows for a sufficiently strong coupling between the atoms and the field [2]. By decreasing the volume of the optical resonator it is possible to reach a regime where a single atom and a single photon interact strongly, forming an atom-photon molecule. This establishes the research field known as cavity quantum electrodynamics (cavity QED) [3][4][5][6][7][8][9] where the atom-light interaction is controlled at its most fundamental level. Integrating the phenomenon of electromagnetically induced transparency (EIT) [10-12] adds additional capabilities such as allowing an opaque cavity QED system to become transparent [13][14][15][16]. The origin of this effect lies in the destructive interference of different absorption paths, preventing light from being absorbed by the system. We exploit this situation with a three-level atom in a Λ-type level configuration (one excited and two ground states) where one branch is strongly coupled to a mode of an optical resonator and the other to an external laser. In the EIT regime, the system remains in a state known as a dark state, since the atom does not absorb light from the fields.Here we show that this scheme can be used to continuously generate light that is genuinely quantum in nature. To this end, we introduce a second laser field which couples the two ground states. As expected for several waves interacting with a nonlinear medium, this gives rise to a new radiation field via an optical wave mixing process [17][18][19][20][21]. Not expected, however, is that if the laser field coupling the atomic ground states is weak enough, the fragile dark states of the cavity EIT system are not destroyed, even when all fields are on resonance with the respective atomic transitions. We then find that the two lasers in combination with the cavity drive transitions between dark states that differ by one photon in the cavity. Thus, the atomic excitation is suppressed due to the destructive interference of the EI...
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