We review studies of the fluctuations of light made accessible by the invention of the laser and the strong interactions realized in cavity QED experiments. Photon antibunching advocating the discrete (particles), is contrasted with amplitude squeezing which speaks of the continuous (waves). The tension between particles and waves is demonstrated by a recent experiment which combines the measurement strategies used to observe these nonclassical behaviors of light [Phys. Rev. Lett. 85, 3149 (2000)].
We review studies of the fluctuations of light made accessible by the invention of the laser and the strong interactions realized in cavity QED experiments. Photon antibunching advocating the discrete (particles), is contrasted with amplitude squeezing which speaks of the continuous (waves). The tension between particles and waves is demonstrated by a recent experiment which combines the measurement strategies used to observe these nonclassical behaviors of light [Phys. Rev. Lett. 85, 3149 (2000)].
As a direct result of the quantum nature of electromagnetic radiation, all forms of light exhibit inherent and unavoidable random fluctuations. Because these fluctuations reveal information about the nature of light and the underlying processes that generate it, they have received considerable attention since the time of Einstein. But they are also a source of noise that limits the accuracy with which information can be transmitted by a beam of light. Although experiments often still struggle with instrumental noise, some are quickly approaching the measurement limits set by the quantum-statistical nature of light. With the help of new techniques to “squeeze” the uncertainty of light, researchers can now conduct experiments with greater precision than possible with laser light. The generation of various forms of squeezed light in recent years has raised hopes for its application to such diverse areas as gravity-wave detection based on optical interferometry and reduced-error lightwave communications.
In classical optics light is considered as an electromagnetic wave, and its dynamical properties are described by the time dependence of amplitude and phase. If a light emerging from a source has random fluctuation of amplitude and phase, this light can be described by a proper ensemble from which the mean and the dispersion of the dynamical variables are calculated. On the other hand, the same light beam can be also considered as a stream of photons in quantum optics, and the wave-particle duality produces nonclassical results in some cases. It is our purpose to clarify the role of wave and particle nature of light and distinguish the classical and quantum effects via the characterization of the dynamical variables when the light goes through a beamsplitter.
Experimental chapter devoted to quantum observables endowed with continuously varying quantum fluctuations, such as position and momentum, quadrature operators, or phase and amplitude of electromagnetic fields . It shows that one can manipulate this quantum noise by generating squeezed states of light, always within the limits imposed by the Heisenberg inequality, and create strong correlations between these observables to conditionally generate quantum states having intensity quantum fluctuations below the "shot noise" limit imposed by the existence of vacuum fluctuations. Describes an experiment dealing with macroscopic mechanical oscillators displaying motional squeezing below the zero point fluctuations, and another one dealing with macroscopic superconducting exhibiting a whole spectrum of strongly nonclassical states, generated by using the strong anharmonicity of the Josephson potential.
One of the most puzzling consequences of interpreting quantum mechanics in terms of concepts borrowed from classical physics, is the so-called wave-particle duality. Usually, wave-particle duality is illustrated in terms of complementarity between path distinguishability and fringe visibility in interference experiments. In this work, we instead propose a new type of complementarity, that between the continuous nature of waves and the discrete character of particles. Using the probabilistic methods of quantum field theory, we show that the simultaneous measurement of the wave amplitude and the number of photons in the same beam of light is, under certain circumstances, prohibited by the laws of quantum mechanics. Our results suggest that the concept of “interferometric duality'' could be eventually replaced by the more general one of “continuous-discrete duality''.
The statistical fluctuations of light can, under certain circumstances, exhibit a number of interesting nonclassical features. These include photon antibunching, sub-Poissonian statistics, and squeezing, all of which exist only in a quantum field. The three effects are distinct, and do not necessarily go together, although the first two are sometimes mistakenly treated as interchangeable. Both photon antibunching and sub-Poissonian statistics have been observed in experiments on resonance fluorescence from single atoms, which is described. Squeezing has not yet been seen experimentally, although many nonlinear processes are expected to give rise to it. The squeezed state can be recognized in heterodyne or homodyne experiments, where the squeezing becomes manifest as sub-Poissonian photon fluctuations.
Coupling on-chip microwave cavities to superconducting microcircuits has provided a new platform to study the light/matter interaction at the most elementary level [1]. The recent generalization of this architecture to more complex open nanocircuits [2,3,4] offers the possibility to go beyond standard cavity quantum electrodynamics experiments usually performed with closed two level systems. A wide variety of experiments can be envisioned, with different types of hybrid nanocircuits combining nanoconductors such as carbon nanotubes or semiconducting nanowires, and metallic electrodes made out from normal metals, superconductors, or ferromagnets. Circuit Quantum Electrodynamics represents a promising method to gain more information on the behavior of electrons in these hybrid nanocircuits. In the first part of this talk, I will discuss the coupling of a Cooper pair splitter to a cavity [5,6]. I will show that a measurement of the cavity dispersive shift provides a rich access to the electronic spectroscopy and dynamics in the Cooper pair splitter [7]. In the second part of this talk, I will discuss the coupling of Majorana quasiparticles (in a semiconducting nanowire) to a cavity [8]. These exotic bound states can cause a significant cavity frequency shift and a strong cavity nonlinearity leading for instance to light squeezing. I will show that the dependence of these effects on the nanowire gate voltages should give direct signatures of the unique properties of Majorana fermions, such as their self-adjoint character and their exponential confinement. References [1] A., Wallraff et al., Nature 431, 162 (2004). [2] M.R. Delbecq et al., Phys. Rev. Lett. 107, 256804 (2011). [3] T. Frey et al., Phys. Rev. Lett. 108, 046807 (2012). [4] K.D. Petersson et al., Nature 490, 380 (2012). [5] A. Cottet, T. Kontos, A. Levy Yeyati, Phys. Rev. Lett. 108, 166803 (2012). [6] A. Cottet, Phys. Rev. B 86, 075107 (2012). [7] A. Cottet et al., in preparation. [8] A. Cottet, T. Kontos, and B. Douçot, arXiv:1307.4185 (2013).