71 research outputs found
Nonclassical radiation from diamond nanocrystals
The quantum properties of the fluorescence light emitted by diamond
nanocrystals containing a single nitrogen-vacancy (NV) colored center is
investigated. We have observed photon antibunching with very low background
light. This system is therefore a very good candidate for the production of
single photon on demand. In addition, we have measured larger NV center
lifetime in nanocrystals than in the bulk, in good agreement with a simple
quantum electrodynamical model.Comment: 8 pages, 5 figures, revised version, to appear in PR
Pure emitter dephasing : a resource for advanced solid-state single photon sources
We have computed the spectrum emitted spontaneously by a quantum dot coupled
to an arbitrarily detuned single mode cavity, taking into account pure
dephasing processes. We show that if the emitter is incoherent, the cavity can
efficiently emit photons with its own spectral characteristics. This effect
opens unique opportunities for the development of devices exploiting both
cavity quantum electrodynamics effects and pure dephasing, such as wavelength
stabilized single photon sources robust against spectral diffusion.Comment: 5 pages, 3 figure
Creating single time-bin entangled photon pairs
When a single emitter is excited by two phase-coherent pulses with a time
delay, each of the pulses can lead to the emission of a photon pair, thus
creating a ``time-bin entangled'' state. Double pair emission can be avoided by
initially preparing the emitter in a metastable state. We show how photons from
separate emissions can be made indistinguishable, permitting their use for
multi-photon interference. Possible realizations are discussed. The method
might also allow the direct creation of n-photon entangled states (n>2).Comment: 4 pages, 1 figur
Quantum Communication with Quantum Dot Spins
Single electron spins in quantum dots are attractive for quantum
communication because of their expected long coherence times. We propose a
method to create entanglement between two remote spins based on the coincident
detection of two photons emitted by the dots. Local nodes of several qubits can
be realized using the dipole-dipole interaction between trions in neighboring
dots and spectral addressing, allowing the realization of quantum repeater
protocols. We have performed a detailed feasibility study of our proposal based
on tight-binding calculations of quantum dot properties.Comment: 4 pages, 2 figures, new and improved version, explicit performance
estimate
Quantum-nondemolition measurements using ghost transitions
International audienceWe present a detailed analysis of the quantum-nondemolition (QND) properties of a measurement scheme employing coherently driven three-level atoms in the Λ or cascade configuration inside an optical cavity. We propose to use a strong signal field to empty one of the transitions and dress the signal-transition levels. The atoms become transparent for the signal beam, which sees a ''ghost transition.'' When a probe is applied and tuned to the vicinity of one of the light-shifted levels, the probe phase is extremely sensitive to fluctuations of the signal intensity. This enhances the QND coupling and enables the system to operate at lower cooperativities
Single photon quantum cryptography
We report the full implementation of a quantum cryptography protocol using a
stream of single photon pulses generated by a stable and efficient source
operating at room temperature. The single photon pulses are emitted on demand
by a single nitrogen-vacancy (NV) color center in a diamond nanocrystal. The
quantum bit error rate is less that 4.6% and the secure bit rate is 9500
bits/s. The overall performances of our system reaches a domain where single
photons have a measurable advantage over an equivalent system based on
attenuated light pulses.Comment: 4 pages, 3 figure
Photon antibunching in the fluorescence of individual color centers in diamond
We have observed photon antibunching in the fluorescence light emitted from a
single N-V center in diamond at room temperature. The possibility of generating
triggerable single photons with such a solide state system is discussedComment: 4 pages, 4 figure
Giant Optical Non-linearity induced by a Single Two-Level System interacting with a Cavity in the Purcell Regime
A two-level system that is coupled to a high-finesse cavity in the Purcell
regime exhibits a giant optical non-linearity due to the saturation of the
two-level system at very low intensities, of the order of one photon per
lifetime. We perform a detailed analysis of this effect, taking into account
the most important practical imperfections. Our conclusion is that an
experimental demonstration of the giant non-linearity should be feasible using
semiconductor micropillar cavities containing a single quantum dot in resonance
with the cavity mode.Comment: 40 pages, 16 figures, accepted in Phys. Rev.
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