Coherent manipulation of a solid-state artificial atom with few photons (original) (raw)

Strong interaction between light and a single trapped atom without a cavity

Many quantum information processing protocols require efficient transfer of quantum information from a flying photon to a stationary quantum system. To transfer information, a photon must first be absorbed by the quantum system. A flying photon can be absorbed by an atom residing in a high-finesse cavity with a probability close to unity. However, it is unclear whether a photon can be absorbed effectively by an atom in a free space. Here, we report on an observation of substantial extinction of a light beam by a single 87 Rb atom through focusing light to a small spot with a single lens. The measured extinction values are not influenced by interference-related effects, and thus can be compared directly to the predictions by existing free-space photon-atom coupling models. Our result opens a new perspective on processing quantum information carried by light using atoms, and is important for experiments that require strong absorption of single photons by an atom in free space.

Coherent control of a solid-state quantum bit with few-photon pulses

arXiv: Quantum Physics, 2015

Single photons are the natural link between the nodes of a quantum network: they coherently propagate and interact with many types of quantum bits including natural and artificial atoms. Ideally, one atom should deterministically control the state of a photon and vice-versa. The interaction between free space photons and an atom is however intrinsically weak and many efforts have been dedicated to develop an efficient interface. Recently, it was shown that the propagation of light can be controlled by an atomic resonance coupled to a cavity or a single mode waveguide. Here we demonstrate that the state of a single artificial atom in a cavity can be efficiently controlled by a few-photon pulse. We study a quantum dot optimally coupled to an electrically-controlled cavity device, acting as a near optimal one-dimensional atom. By monitoring the exciton population through resonant fluorescence, we demonstrate Rabi oscillations with a pi\pipi-pulse of only 3.8 photons on average. The proba...

A Nanophotonic Quantum Phase Switch with a Single Atom

Frontiers in Optics 2014, 2014

In analogy to transistors in classical electronic circuits, a quantum optical switch is an important element of quantum circuits and quantum networks [1][2]. Operated at the fundamental limit where a single quantum of light or matter controls another field or material system[4], it may enable fascinating applications such as long-distance quantum communication , distributed quantum information processing[2] and metrology , and the exploration of novel quantum states of matter . Here, by strongly coupling a photon to a single atom trapped in the near field of a nanoscale photonic crystal cavity, we realize a system where a single atom switches the phase of a photon, and a single photon modifies the atom's phase. We experimentally demonstrate an atom-induced optical phase shift[8] that is nonlinear at the two-photon level[9], a photon number router that separates individual photons and photon pairs into different output modes[10], and a single-photon switch where a single "gate" photon controls the propagation of a subsequent probe field 12]. These techniques pave the way towards integrated quantum nanophotonic networks involving multiple atomic nodes connected by guided light.

A solid-state light–matter interface at the single-photon level

Nature, 2008

Coherent and reversible mapping of quantum information between light and matter is an important experimental challenge in quantum information science. In particular, it is a decisive milestone for the implementation of quantum networks and quantum repeaters . So far, quantum interfaces between light and atoms have been demonstrated with atomic gases , and with single trapped atoms in cavities . Here we demonstrate the coherent and reversible mapping of a light field with less than one photon per pulse onto an ensemble of ∼ 10 7 atoms naturally trapped in a solid. This is achieved by coherently absorbing the light field in a suitably prepared solid state atomic medium . The state of the light is mapped onto collective atomic excitations on an optical transition and stored for a pre-programmed time up of to 1µs before being released in a well defined spatio-temporal mode as a result of a collective interference. The coherence of the process is verified by performing an interference experiment with two stored weak pulses with a variable phase relation. Visibilities of more than 95% are obtained, which demonstrates the high coherence of the mapping process at the single photon level. In addition, we show experimentally that our interface allows one to store and retrieve light fields in multiple temporal modes. Our results represent the first observation of collective enhancement at the single photon level in a solid and open the way to multimode solid state quantum memories as a promising alternative to atomic gases.

Towards quantum computing with single atoms and optical cavities on atom chips

Journal of Modern Optics, 2007

We report on recent developments in the integration of optical microresonators into atom chips and describe some fabrication and implementation challenges. We also review theoretical proposals for quantum computing with single atoms based on the observation of photons leaking through the cavity mirrors. The use of measurements to generate entanglement can result in simpler, more robust and scalable quantum computing architectures. Indeed, we show that quantum computing with atom-cavity systems is feasible even in the presence of relatively large spontaneous decay rates and finite photon detector efficiencies.

Photon-Mediated Interactions Between Distant Artificial Atoms

Science, 2013

Photon-mediated interactions between atoms are of fundamental importance in quantum optics, quantum simulations and quantum information processing. The exchange of real and virtual photons between atoms gives rise to non-trivial interactions the strength of which decreases rapidly with distance in three dimensions.

Quantum Manipulation Using Light-Atom Interaction

rle.mit.edu

Interactions between weak optical pulses at the single-photon level represent the fundamental limit of nonlinear optical science, and reaching this regime has been a long-standing goal, investigated over the last three decades [1]. In addition to fundamental ...

Atoms versus photons as carriers of quantum states

Physical Review A, 2013

The problem of the complete transfer of quantum states and entanglement in a four-qubit system composed of two single-mode cavities and two two-level atoms is investigated. The transfer of single and double excitation states is discussed for two different coupling configurations between the qubits. In the first, the coupling is mediated by the atoms that simultaneously couple to the cavity modes. In the second configuration, each atom resides inside one of the cavities and the coupling between the cavities is mediated by the overlapping field modes. A proper choice of basis states makes it possible to identify states that could be completely transferred between themselves. Simple expressions are derived for the conditions for the complete transfer of quantum states and entanglement. These conditions impose severe constraints on the evolution of the system in the form of constants of motion. The constrains on the evolution of the system imply that not all states can evolve in time, and we find that the evolution of the entire system can be confined into that occurring among two states only. Detailed analysis show that in the case where the interaction is mediated by the atoms, only symmetric superposition states can be completely and reversibly transferred between the atoms and the cavity modes. In the case where the interaction is mediated by the overlapping field modes, both symmetric and antisymmetric superposition states can be completely transferred. We also show that the system is capable of generating purely photonic NOON states, but only if the coupling is mediated by the atoms, and demonstrate that the ability to generate the NOON states relies on perfect transfer of an entanglement from the atoms to the cavity modes.

Photon bound state dynamics from a single artificial atom

Nature Physics

The interaction between photons and a single two-level atom constitutes a fundamental paradigm in quantum physics. The nonlinearity provided by the atom leads to a strong dependence of the light–matter interface on the number of photons interacting with the two-level system within its emission lifetime. This nonlinearity unveils strongly correlated quasiparticles known as photon bound states, giving rise to key physical processes such as stimulated emission and soliton propagation. Although signatures consistent with the existence of photon bound states have been measured in strongly interacting Rydberg gases, their hallmark excitation-number-dependent dispersion and propagation velocity have not yet been observed. Here we report the direct observation of a photon-number-dependent time delay in the scattering off a single artificial atom—a semiconductor quantum dot coupled to an optical cavity. By scattering a weak coherent pulse off the cavity–quantum electrodynamics system and mea...

A single-photon server with just one atom

Nature Physics, 2007

Neutral atoms are ideal objects for the deterministic processing of quantum information. Entanglement operations have been performed by photon exchange or controlled collisions. Atom-photon interfaces were realized with single atoms in free space or strongly coupled to an optical cavity. A long standing challenge with neutral atoms, however, is to overcome the limited observation time. Without exception, quantum effects appeared only after ensemble averaging. Here we report on a single-photon source with one-and-only-one atom quasi permanently coupled to a high-finesse cavity. Quasi permanent refers to our ability to keep the atom long enough to, first, quantify the photon-emission statistics and, second, guarantee the subsequent performance as a single-photon server delivering up to 300,000 photons for up to 30 seconds. This is achieved by a unique combination of single-photon generation and atom cooling. Our scheme brings truly deterministic protocols of quantum information science with light and matter within reach.