[Show abstract][Hide abstract] ABSTRACT: We demonstrate coherent control of single-photon absorption and reemission in a two-level cold atomic ensemble. This is achieved by interfering the incident single-photon wave packet with the emission (or scattering) wave. For a photon with an exponential growth waveform with a time constant equal to the excited-state lifetime, we observe that the single-photon emission probability during the absorption can be suppressed due to the perfect destructive interference. After the incident photon waveform is switched off, the absorbed photon is then reemitted to the same spatial mode as that of the incident photon with an efficiency of 20%. For a photon with an exponential decay waveform with the same time constant, both the absorption and reemission occur within the waveform duration. Our experimental results suggest that the absorption and emission of a single photon in a two-level atomic ensemble may possibly be manipulated by shaping its waveform in the time domain.
[Show abstract][Hide abstract] ABSTRACT: We demonstrate a miniature source of long biphotons utilizing the cluster effect and double-pass pumping in a monolithic doubly resonant parametric down-converter. We obtain a biphoton correlation time of 17.1 ns with a generation rate of 1.10×105 biphotons/(s mW) and an estimated linewidth of 8.3 MHz.
[Show abstract][Hide abstract] ABSTRACT: An ultrabright compact source of long biphotons is essential for
scalable quantum networks. Here we report the generation of long
biphotons utilizing the cluster effect in a monolithic doubly resonant
parametric down-converter. The biphoton generation rate and spectral
brightness are 110 and 41 times larger, respectively, than previously
reported. This source will find applications in quantum repeater
[Show abstract][Hide abstract] ABSTRACT: We calculate the properties of a biphoton source based on resonant
backward-wave spontaneous parametric down-conversion. We show that the
biphotons are generated in a single longitudinal mode having a subnatural
linewidth and a Glauber correlation time exceeding 65 ns.
Physical Review A 05/2011; 83(6). · 3.04 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We describe a proof-of-principal experiment demonstrating the use of spread spectrum technology at the single photon level. We show how single photons with a prescribed temporal shape, in the presence of interfering noise, may be hidden and recovered.
[Show abstract][Hide abstract] ABSTRACT: We describe a proof-of-principal experiment demonstrating a Fourier technique
for measuring the shape of biphoton wavepackets. The technique is based on the
use of synchronously driven fast modulators and slow (integrating) detectors.
[Show abstract][Hide abstract] ABSTRACT: We study the suppression of noise-induced phase decoherence in a single atomic qubit by employing pulse sequences. The atomic qubit is composed of a single neutral atom in a far-detuned optical dipole trap and the phase decoherence may originate from the laser intensity and beam pointing fluctuations as well as magnetic field fluctuations. We show that suitable pulse sequences may prolongate the qubit coherence time substantially as comparing to the conventional spin echo pulse. Comment: 4 pages, 3 figures
[Show abstract][Hide abstract] ABSTRACT: Scalable quantum-information processing requires the capability of storing quantum states. In particular, a long-lived storable and retrievable quantum memory for single excitations is of key importance to long-distance quantum communication with atomic ensembles and linear optics. Although atomic memories for classical light and continuous variables have been demonstrated with millisecond storage time, lifetimes of only around 10 s have been reported for quantum memories storing single excitations. Here we present an experimental investigation into extending the storage time of quantum memory for single excitations. We identify and isolate distinct mechanisms responsible for the decoherence of spin waves in atomic-ensemble-based quantum memories. By exploiting magnetic-field-insensitive states—so-called clock states—and generating a long-wavelength spin wave to suppress dephasing, we succeed in extending the storage time of the quantum memory to 1 ms. Our result represents an important advance towards long-distance quantum communication and should provide a realistic approach to large-scale quantum information processing.
[Show abstract][Hide abstract] ABSTRACT: We report the experimental demonstration of quantum memory for collective atomic states in a far-detuned optical dipole trap. Generation of the collective atomic state is heralded by the detection of a Raman scattered photon and accompanied by storage in the ensemble of atoms. The optical dipole trap provides confinement for the atoms during the quantum storage while retaining the atomic coherence. We probe the quantum storage by cross correlation of the photon pair arising from the Raman scattering and the retrieval of the atomic state stored in the memory. Nonclassical correlations are observed for storage times up to 60 mus.
[Show abstract][Hide abstract] ABSTRACT: The combination of quantum teleportation and quantum memory of photonic qubits is essential for future implementations of large-scale quantum communication and measurement-based quantum computation. Both steps have been achieved separately in many proof-of-principle experiments, but the demonstration of memory-built-in teleportation of photonic qubits remains an experimental challenge. Here, we demonstrate teleportation between photonic (flying) and atomic (stationary) qubits. In our experiment, an unknown polarization state of a single photon is teleported over 7 m onto a remote atomic qubit that also serves as a quantum memory. The teleported state can be stored and successfully read out for up to 8 micro-second. Besides being of fundamental interest, teleportation between photonic and atomic qubits with the direct inclusion of a readable quantum memory represents a step towards an efficient and scalable quantum network.