25 research outputs found
Nondestructive Detection of an Optical Photon
All optical detectors to date annihilate photons upon detection, thus
excluding repeated measurements. Here, we demonstrate a robust photon detection
scheme which does not rely on absorption. Instead, an incoming photon is
reflected off an optical resonator containing a single atom prepared in a
superposition of two states. The reflection toggles the superposition phase
which is then measured to trace the photon. Characterizing the device with
faint laser pulses, a single-photon detection efficiency of 74% and a survival
probability of 66% is achieved. The efficiency can be further increased by
observing the photon repeatedly. The large single-photon nonlinearity of the
experiment should enable the development of photonic quantum gates and the
preparation of novel quantum states of light.Comment: published online in Science Express, 14 November 201
Erbium dopants in silicon nanophotonic waveguides
The combination of established nanofabrication with attractive material
properties makes silicon a promising material for quantum technologies, where
implanted dopants serve as qubits with high density and excellent coherence
even at elevated temperatures. In order to connect and control these qubits,
interfacing them with light in nanophotonic waveguides offers unique promise.
Here, we present resonant spectroscopy of implanted erbium dopants in such
waveguides. We overcome the requirement of high doping and above-bandgap
excitation that limited earlier studies. We thus observe erbium incorporation
at well-defined lattice sites with a thousandfold reduced inhomogeneous
broadening of about 1 GHz and a spectral diffusion linewidth down to 45 MHz.
Our study thus introduces a novel materials platform for the implementation of
on-chip quantum memories, microwave-to-optical conversion, and distributed
quantum information processing, with the unique feature of operation in the
main wavelength band of fiber-optic communication.Comment: 7 pages, 4 figure
Dynamical decoupling of spin ensembles with strong anisotropic interactions
Ensembles of dopants have widespread applications in quantum technology. The
miniaturization of corresponding devices is however hampered by dipolar
interactions that reduce the coherence at increased dopant density. We
theoretically and experimentally investigate this limitation. We find that
dynamical decoupling can alleviate, but not fully eliminate, the decoherence in
crystals with strong anisotropic spin-spin interactions. Our findings can be
generalized to all quantum systems with anisotropic g-factor used for quantum
sensing, microwave-to-optical conversion, and quantum memory.Comment: Second version of the manuscript contains additional measurements, in
which dynamical decoupling in the absence of strong spin-spin interactions is
demonstrate
Heralded Storage of a Photonic Quantum Bit in a Single Atom
Combining techniques of cavity quantum electrodynamics, quantum measurement,
and quantum feedback, we have realized the heralded transfer of a polarization
qubit from a photon onto a single atom with 39% efficiency and 86% fidelity.
The reverse process, namely, qubit transfer from the atom onto a given photon,
is demonstrated with 88% fidelity and an estimated efficiency of up to 69%. In
contrast to previous work based on two-photon interference, our scheme is
robust against photon arrival-time jitter and achieves much higher
efficiencies. Thus, it constitutes a key step toward the implementation of a
long-distance quantum network.Comment: 6 pages, 4 figure
Cavity-based quantum networks with single atoms and optical photons
Distributed quantum networks will allow users to perform tasks and to
interact in ways which are not possible with present-day technology. Their
implementation is a key challenge for quantum science and requires the
development of stationary quantum nodes that can send and receive as well as
store and process quantum information locally. The nodes are connected by
quantum channels for flying information carriers, i.e. photons. These channels
serve both to directly exchange quantum information between nodes as well as to
distribute entanglement over the whole network. In order to scale such networks
to many particles and long distances, an efficient interface between the nodes
and the channels is required. This article describes the cavity-based approach
to this goal, with an emphasis on experimental systems in which single atoms
are trapped in and coupled to optical resonators. Besides being conceptually
appealing, this approach is promising for quantum networks on larger scales, as
it gives access to long qubit coherence times and high light-matter coupling
efficiencies. Thus, it allows one to generate entangled photons on the push of
a button, to reversibly map the quantum state of a photon onto an atom, to
transfer and teleport quantum states between remote atoms, to entangle distant
atoms, to detect optical photons nondestructively, to perform entangling
quantum gates between an atom and one or several photons, and even provides a
route towards efficient heralded quantum memories for future repeaters. The
presented general protocols and the identification of key parameters are
applicable to other experimental systems.Comment: in Rev. Mod. Phys. (2015
Purcell enhancement of single-photon emitters in silicon
Individual spins that are coupled to telecommunication photons offer unique
promise for distributed quantum information processing once a coherent and
efficient spin-photon interface can be fabricated at scale. We implement such
an interface by integrating erbium dopants into a nanophotonic silicon
resonator. We achieve spin-resolved excitation of individual emitters with <
0.1 GHz spectral diffusion linewidth. Upon resonant driving, we observe optical
Rabi oscillations and single-photon emission with a 78-fold Purcell
enhancement. Our results establish a promising new platform for quantum
networks
Efficient Teleportation between Remote Single-Atom Quantum Memories
We demonstrate teleportation of quantum bits between two single atoms in
distant laboratories. Using a time-resolved photonic Bell-state measurement, we
achieve a teleportation fidelity of (88.0+/-1.5)%, largely determined by our
entanglement fidelity. The low photon collection efficiency in free space is
overcome by trapping each atom in an optical cavity. The resulting success
probability of 0.1% is almost 5 orders of magnitude larger than in previous
experiments with remote material qubits. It is mainly limited by photon
propagation and detection losses and can be enhanced with a cavity-based
deterministic Bell-state measurement.Comment: 7 pages, 4 figures, 1 tabl
Laser stabilization to a cryogenic fiber ring resonator
The frequency stability of lasers is limited by thermal noise in
state-of-the-art frequency references. Further improvement requires operation
at cryogenic temperature. In this context, we investigate a fiber-based ring
resonator. Our system exhibits a first-order temperature-insensitive point
around K, much lower than that of crystalline silicon. The observed low
sensitivity with respect to vibrations (), temperature () and
pressure changes () makes our approach
promising for future precision experiments
Generation of single photons from an atom-cavity system
A single rubidium atom trapped within a high-finesse optical cavity is an
efficient source of single photons. We theoretically and experimentally study
single-photon generation using a vacuum stimulated Raman adiabatic passage. We
experimentally achieve photon generation efficiencies of up to 34% and 56% on
the D1 and D2 line, respectively. Output coupling with 89% results in
record-high efficiencies for single photons in one spatiotemporally
well-defined propagating mode. We demonstrate that the observed generation
efficiencies are constant in a wide range of applied pump laser powers and
virtual level detunings. This allows for independent control over the frequency
and wave packet envelope of the photons without loss in efficiency. In
combination with the long trapping time of the atom in the cavity, our system
constitutes a significant advancement toward an on-demand, highly efficient
single-photon source for quantum information processing tasks.Comment: 7 pages, 5 figure
Narrow optical transitions in erbium-implanted silicon waveguides
The realization of a scalable architecture for quantum information processing
is a major challenge for quantum science. A promising approach is based on
emitters in nanostructures that are coupled by light. Here, we show that erbium
dopants can be reproducibly integrated at well-defined lattice sites by
implantation into pure silicon. We thus achieve a narrow inhomogeneous
broadening, less than 1 GHz, strong optical transitions, and an outstanding
optical coherence even at temperatures of 8 K, with an upper bound to the
homogeneous linewidth of around 10 kHz. Our study thus introduces a promising
materials platform for the implementation of on-chip quantum memories,
microwave-to-optical conversion, and distributed quantum information
processing