37 research outputs found
An optical modulator based on a single strongly coupled quantum dot - cavity system in a p-i-n junction
We demonstrate an optical modulator based on a single quantum dot strongly coupled to a photonic crystal cavity. A vertical p-i-n junction is used to tune the quantum dot and thereby modulate the cavity transmission, with a measured instrument-limited response time of 13 ns. A modulator based on a single quantum dot promises operation at high bandwidth and low power
Local On-Chip Temperature Tuning of InGaAs Quantum Dots
Quantum network based on InGaAs quantum dots (QDs) rely on QDs being in resonance with each other. We developed a new technique based on temperature tuning to spectrally align QDs located on the same chip
Local Quantum Dot Tuning on Photonic Crystal Chips
Quantum networks based on InGaAs quantum dots embedded in photonic crystal
devices rely on QDs being in resonance with each other and with the cavities
they are embedded in. We developed a new technique based on temperature tuning
to spectrally align different quantum dots located on the same chip. The
technique allows for up to 1.8nm reversible on-chip quantum dot tuning
Resonant Excitation of a Quantum Dot Strongly Coupled to a Photonic Crystal Nanocavity
We describe the resonant excitation of a single quantum dot that is strongly coupled to a photonic crystal nanocavity. The cavity represents a spectral window for resonantly probing the optical transitions of the quantum dot. We observe narrow absorption lines attributed to the single and biexcition quantum dot transitions and measure antibunched population of the detuned cavity mode [g^(2)(0)=0.19]
Ultra Fast Nonlinear Optical Tuning of Photonic Crystal Cavities
We demonstrate fast (up to 20 GHz), low power (5 ) modulation of
photonic crystal (PC) cavities in GaAs containing InAs quantum dots. Rapid
modulation through blue-shifting of the cavity resonance is achieved via free
carrier injection by an above-band picosecond laser pulse. Slow tuning by
several linewidths due to laser-induced heating is also demonstrated
Controlled Phase Shifts with a Single Quantum Dot
Optical nonlinearities enable photon-photon interaction and lie at the heart of several proposals for quantum information processing, quantum nondemolition measurements of photons, and optical signal processing. To date, the largest nonlinearities have been realized with single atoms and atomic ensembles. We show that a single quantum dot coupled to a photonic crystal nanocavity can facilitate controlled phase and amplitude modulation between two modes of light at the single-photon level. At larger control powers, we observed phase shifts up to π/4 and amplitude modulation up to 50%. This was accomplished by varying the photon number in the control beam at a wavelength that was the same as that of the signal, or at a wavelength that was detuned by several quantum dot linewidths from the signal. Our results present a step toward quantum logic devices and quantum nondemolition measurements on a chip
High resolution coherent population trapping on a single hole spin in a semiconductor
We report high resolution coherent population trapping on a single hole spin
in a semiconductor quantum dot. The absorption dip signifying the formation of
a dark state exhibits an atomic physics-like dip width of just 10 MHz. We
observe fluctuations in the absolute frequency of the absorption dip, evidence
of very slow spin dephasing. We identify this process as charge noise by,
first, demonstrating that the hole spin g-factor in this configuration
(in-plane magnetic field) is strongly dependent on the vertical electric field,
and second, by characterizing the charge noise through its effects on the
optical transition frequency. An important conclusion is that charge noise is
an important hole spin dephasing process
Local tuning of photonic crystal cavities using chalcogenide glasses
We demonstrate a method to locally change the refractive index in planar
optical devices by photodarkening of a thin chalcogenide glass layer deposited
on top of the device. The method is used to tune the resonance of GaAs-based
photonic crystal cavities by up to 3 nm at 940 nm, with only 5% deterioration
in cavity quality factor. The method has broad applications for postproduction
tuning of photonic devices.Financial support was provided by ONR Young Investigator
Award, the MURI Center for photonic quantum information
systems ARO/DTO Program No. DAAD19-03-1-
0199, and NSF Grant No. CCF-0507295. Work was
performed in part at the Stanford Nanofabrication Facility of
NNIN supported by the National Science Foundation under
Grant No. ECS-9731293. CUDOS is an Australian Research
Council Centre of Excellence
Single-emitter quantum key distribution over 175 km of fiber with optimised finite key rates
Quantum key distribution with solid-state single-photon emitters is gaining
traction due to their rapidly improving performance and compatibility with
future quantum network architectures. In this work, we perform fibre-based
quantum key distribution with a quantum dot frequency-converted to telecom
wavelength, achieving count rates of 1.6 MHz with
. We demonstrate positive key rates
up to 175 km in the asymptotic regime. We then show that the community standard
analysis for non-decoy state QKD drastically overestimates the acquisition time
required to generate secure finite keys. Our improved analysis using the
multiplicative Chernoff bound reduces the required number of received signals
by a factor of over existing work, with the finite key rate approaching
the asymptotic limit at all achievable distances for acquisition times of one
hour. Over a practical distance of 100 km we achieve a finite key rate of 13
kbps after one minute of integration time. This result represents major
progress towards the feasibility of long-distance single-emitter QKD networks.Comment: 9 pages, 3 figure