160 research outputs found
Enhanced single-photon emission from a quantum dot in a micropost microcavity
We demonstrate a single-photon source based on a quantum dot in a micropost
microcavity that exhibits a large Purcell factor together with a small
multi-photon probability. For a quantum dot on resonance with the cavity, the
spontaneous emission rate is increased by a factor of five, while the
probability to emit two or more photons in the same pulse is reduced to 2%
compared to a Poisson-distributed source of the same intensity. In addition to
the small multi-photon probability, such a strong Purcell effect is important
in a single-photon source for improving the photon outcoupling efficiency and
the single-photon generation rate, and for bringing the emitted photon pulses
closer to the Fourier transform limit.Comment: 4 pages, 3 figure
Nonlocal quantum information in bipartite quantum error correction
We show how to convert an arbitrary stabilizer code into a bipartite quantum code. A bipartite quantum code is one that involves two senders and one receiver. The two senders exploit both nonlocal and local quantum resources to encode quantum information with local encoding circuits. They transmit their encoded quantum data to a single receiver who then decodes the transmitted quantum information. The nonlocal resources in a bipartite code are ebits and nonlocal information qubits, and the local resources are ancillas and local information qubits. The technique of bipartite quantum error correction is useful in both the quantum communication scenario described above and in fault-tolerant quantum computation. It has application in fault-tolerant quantum computation because we can prepare nonlocal resources offline and exploit local encoding circuits. In particular, we derive an encoding circuit for a bipartite version of the Steane code that is local and additionally requires only nearest-neighbor interactions. We have simulated this encoding in the CNOT extended rectangle with a publicly available fault-tolerant simulation software. The result is that there is an improvement in the pseudothreshold with respect to the baseline Steane code, under the assumption that quantum memory errors occur less frequently than quantum gate errors. © 2010 Springer Science+Business Media, LLC
Entanglement formation and violation of Bell's inequality with a semiconductor single photon source
We report the generation of polarization-entangled photons, using a quantum
dot single photon source, linear optics and photodetectors. Two photons created
independently are observed to violate Bell's inequality. The density matrix
describing the polarization state of the postselected photon pairs is also
reconstructed, and agrees well with a simple model predicting the quality of
entanglement from the known parameters of the single photon source. Our scheme
provides a method to generate no more than one entangled photon pair per cycle,
a feature useful to enhance quantum cryptography protocols using entangled
photons.Comment: 4 pages, 3 figures, submitted to PR
On the indistinguishability of Raman photons
We provide a theoretical framework to study the effect of dephasing on the
quantum indistinguishability of single photons emitted from a coherently driven
cavity QED -system. We show that with a large excited-state detuning,
the photon indistinguishability can be drastically improved provided that the
fluctuation rate of the noise source affecting the excited state is fast
compared with the photon emission rate. In some cases a spectral filter is
required to realize this improvement, but the cost in efficiency can be made
small.Comment: 18 pages, 3 figures, final versio
Devices and architectures for large scale integrated silicon photonics circuits
We present DWDM nanophotonics architectures based on microring resonator modulators and detectors. We focus on two implementations: an on chip interconnect for multicore processor (Corona) and a high radix network switch (HyperX). Based on the requirements of these applications we discuss the key constraints on the photonic circuits' devices and fabrication techniques as well as strategies to improve their performance
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