H. Jeff Kimble

Functional Quantum Nodes for Entanglement Distribution over Scalable Quantum Networks

We demonstrated entanglement distribution between two remote quantum nodes located 3 meters apart. This distribution involves the asynchronous preparation of two pairs of atomic memories and the coherent mapping of stored atomic states into light fields in an effective state of near-maximum polarization entanglement. Entanglement is verified by way of the measured violation of a Bell inequality, and it can be used for communication protocols such as quantum cryptography. The demonstrated quantum nodes and channels can be used as segments of a quantum repeater, providing an essential tool for robust long-distance quantum communication.

Efficient retrieval of a single excitation stored in an atomic ensemble

We report significant improvements in the retrieval efficiency of a single excitation stored in an atomic ensemble and in the subsequent generation of strongly correlated pairs of photons. A 50% probability of transforming the stored excitation into one photon in a well-defined spatio-temporal mode at the output of the ensemble is demonstrated. These improvements are illustrated by the generation of high-quality heralded single photons with a suppression of the two-photon component below 1% of the value for a coherent state. A broad characterization of our system is performed for different parameters in order to provide input for the future design of realistic quantum networks.

Neoclassical Light - An Assessment of the Voyage into Hilbert Space

I thank Rodger Walser and his colleagues for organizing this conference to celebrate George Sudarshan’s birthday and landmark achievements in science. It is an honor for me to be here and also a great pleasure to be back in Austin to join the chorus of the FOGS. I would like begin with a brief historical introduction and then turn to topics that we haven’t heard so much about thus far in the symposium, namely experiments in Quantum Optics. Let me remind you that blackbody radiation has had a profound impact on physics since the time of Planck. However, even in more modern times after the development of quantum mechanics and quantum electrodynamics, one really did not know how to describe the underlying field fluctuations as required for diverse interference phenomena. Emil Wolf laid critical foundations for this enterprise with his theory of classical coherence developed in collaboration with Max Born in their classic book Principles of Optics. A great challenge to the physics community was the experiment by R. H. Brown and R. Q. Twiss in 1956 [1], which led to a confusing and controversial time for photons and fields. In 1958 Leonard Mandel helped to resolve the controversy by explaining how light fluctuations are converted to photocurrents in the detection process, albeit in with a classical description of the field [2]. The confusion arose from the effort to understand, on the one hand, interference phenomena that are expressed in terms of the complex amplitude of the electromagnetic field, for which only a classical description was available. On the other hand, quantum electrodynamics had been developed based upon energy eigenstates (i.e., Fock states) with photons as quanta. It was really difficult to understand how the electric and magnetic fields behave in terms of these quantum states. For example, the expectation value of any electromagnetic field is zero in a Fock state. The confusion was compounded by the historic invention of the maser and laser and by the pressing need for quantum theories of the dynamical processes of these and other laboratory advances.

Quantum networks enabled by quantum optics

Summary form only given. Quantum networks offer opportunities for the exploration of physical systems that have not heretofore existed in the natural world with applications to quantum computation, communication, metrology, and quantum many-body physics [1]. As illustrated in Fig. 1, a quantum network is created by generating and storing quantum states locally in quantum nodes. These nodes interact over quantum channels to enable entanglement to be spread across the network.In my presentation [2], I will provide an overview of quantum networks from formal to physical. I will discuss research at Caltech for the laboratory realization of small networks composed of atoms that interact strongly by way of single photons [3-6]. The goal is to achieve lithographic quantum optical circuits, for which atoms are trapped near microand nano-scopic dielectric structures and “wired” together by photons propagating through the circuit elements. Single atoms and atomic ensembles can endow quantum functionality for otherwise linear optical circuits and thereby the capability to build quantum networks component by component.

Characterizing Multipartite Entanglement with Uncertainty Relations

We report the characterization of multipartite photonic entanglement consisting of a single photon shared among four optical paths using uncertainty relations. We discuss an extension of this method to detect entanglement of four atomic ensembles.

Strong Interactions of Single Atoms and Photons with Toroidal Micro-Resonators

Strong radiative coupling between one atom and photon has been achieved with high-Q micro-toroidal resonators, thereby providing capabilities for diverse advances in quantum information science, including an efficient router for single photons and atom-atom interactions catalyzed by one photon. Article not available.

Nonclassical Light for Quantum Information Science

Over the past several decades, the Quantum Optics community has generated a zoology of manifestly quantum or nonclassical states of the electromagnetic field. Beyond a historical significance in physics, nonclassical light is playing a leading role in Quantum Information Science, including for quantum computation, communication, and metrology. My tutorial will provide an overview of nonclassical light, from generation to identification to application.

Measurement and control of single atom motions in the quantum regime

Using cold atoms strongly coupled to a high finesse optical cavity, we have performed real-time continuous measurement of single atomic trajectories in terms of the interaction energy (Eint) with the cavity. Individual transit events reveal a shot-noise limited measurement (fractional) sensitivity of 4×10−4/Hz to variations in Eint/ℏ within a bandwidth of 1–300 kHz. The strong coupling of atom and cavity leads to a maximum interaction energy greater than the kinetic energy of an intracavity laser-cooled atom, even under weak cavity excitation. Evidence of mechanical light forces for intracavity photon number <1 has been observed. The quantum character of the nonlinear optical response of the atom-cavity system is manifested for the trajectory of a single atom.

Quantum information processing with cavity QED

Strongly coupled cavity QED systems show great promise for coherent processing of quantum information in the contexts of quantum computing, communication and cryptography. We present here current progress in experiments for which single atoms are strongly coupled to the mode of a high finesse optical resonator.

Nonclassical Field Correlations in Quantum Optics

The manifestly quantum or nonclassical character of the electromagnetic field is investigated in several optical experiments. Nonclassical correlations as manifest in measurements of photon statistics and of quadrature phase amplitudes offer possibilities for detection strategies with sensitivity beyond the vacuum-state limit and for quantitative studies of quantum state reduction in a dissipative setting.