17,793 research outputs found
Mapping multiple photonic qubits into and out of one solid-state atomic ensemble
The future challenge of quantum communication are scalable quantum networks,
which require coherent and reversible mapping of photonic qubits onto
stationary atomic systems (quantum memories). A crucial requirement for
realistic networks is the ability to efficiently store multiple qubits in one
quantum memory. Here we demonstrate coherent and reversible mapping of 64
optical modes at the single photon level in the time domain onto one
solid-state ensemble of rare-earth ions. Our light-matter interface is based on
a high-bandwidth (100 MHz) atomic frequency comb, with a pre-determined storage
time of 1 microseconds. We can then encode many qubits in short <10 ns temporal
modes (time-bin qubits). We show the good coherence of the mapping by
simultaneously storing and analyzing multiple time-bin qubits.Comment: 7 pages, 6 figures + Supplementary materia
The Simulation of Read-time Scalable Coherent Interface
Scalable Coherent Interface (SCI, IEEE/ANSI Std 1596-1992) (SCI1, SCI2) is a high performance interconnect for shared memory multiprocessor systems. In this project we investigate an SCI Real Time Protocols (RTSCI1) using Directed Flow Control Symbols. We studied the issues of efficient generation of control symbols, and created a simulation model of the protocol on a ring-based SCI system. This report presents the results of the study. The project has been implemented using SES/Workbench. The details that follow encompass aspects of both SCI and Flow Control Protocols, as well as the effect of realistic client/server processing delay. The report is organized as follows. Section 2 provides a description of the simulation model. Section 3 describes the protocol implementation details. The next three sections of the report elaborate on the workload, results and conclusions. Appended to the report is a description of the tool, SES/Workbench, used in our simulation, and internal details of our implementation of the protocol
The Quantum Internet
Quantum networks offer a unifying set of opportunities and challenges across
exciting intellectual and technical frontiers, including for quantum
computation, communication, and metrology. The realization of quantum networks
composed of many nodes and channels requires new scientific capabilities for
the generation and characterization of quantum coherence and entanglement.
Fundamental to this endeavor are quantum interconnects that convert quantum
states from one physical system to those of another in a reversible fashion.
Such quantum connectivity for networks can be achieved by optical interactions
of single photons and atoms, thereby enabling entanglement distribution and
quantum teleportation between nodes.Comment: 15 pages, 6 figures Higher resolution versions of the figures can be
downloaded from the following link:
http://www.its.caltech.edu/~hjkimble/QNet-figures-high-resolutio
Quantum interface between frequency-uncorrelated down-converted entanglement and atomic-ensemble quantum memory
Photonic entanglement source and quantum memory are two basic building blocks
of linear-optical quantum computation and long-distance quantum communication.
In the past decades, intensive researches have been carried out, and remarkable
progress, particularly based on the spontaneous parametric down-converted
(SPDC) entanglement source and atomic ensembles, has been achieved. Currently,
an important task towards scalable quantum information processing (QIP) is to
efficiently write and read entanglement generated from a SPDC source into and
out of an atomic quantum memory. Here we report the first experimental
realization of a quantum interface by building a 5 MHz frequency-uncorrelated
SPDC source and reversibly mapping the generated entangled photons into and out
of a remote optically thick cold atomic memory using electromagnetically
induced transparency. The frequency correlation between the entangled photons
is almost fully eliminated with a suitable pump pulse. The storage of a
triggered single photon with arbitrary polarization is shown to reach an
average fidelity of 92% for 200 ns storage time. Moreover,
polarization-entangled photon pairs are prepared, and one of photons is stored
in the atomic memory while the other keeps flying. The CHSH Bell's inequality
is measured and violation is clearly observed for storage time up to 1
microsecond. This demonstrates the entanglement is stored and survives during
the storage. Our work establishes a crucial element to implement scalable
all-optical QIP, and thus presents a substantial progress in quantum
information science.Comment: 28 pages, 4 figures, 1 tabl
Cavity QED with atomic mirrors
A promising approach to merge atomic systems with scalable photonics has
emerged recently, which consists of trapping cold atoms near tapered
nanofibers. Here, we describe a novel technique to achieve strong, coherent
coupling between a single atom and photon in such a system. Our approach makes
use of collective enhancement effects, which allow a lattice of atoms to form a
high-finesse cavity within the fiber. We show that a specially designated
"impurity" atom within the cavity can experience strongly enhanced interactions
with single photons in the fiber. Under realistic conditions, a "strong
coupling" regime can be reached, wherein it becomes feasible to observe vacuum
Rabi oscillations between the excited impurity atom and a single cavity
quantum. This technique can form the basis for a scalable quantum information
network using atom-nanofiber systems.Comment: 20 pages, 4 figure
Superconducting Gatemon Qubit based on a Proximitized Two-Dimensional Electron Gas
The coherent tunnelling of Cooper pairs across Josephson junctions (JJs)
generates a nonlinear inductance that is used extensively in quantum
information processors based on superconducting circuits, from setting qubit
transition frequencies and interqubit coupling strengths, to the gain of
parametric amplifiers for quantum-limited readout. The inductance is either set
by tailoring the metal-oxide dimensions of single JJs, or magnetically tuned by
parallelizing multiple JJs in superconducting quantum interference devices
(SQUIDs) with local current-biased flux lines. JJs based on
superconductor-semiconductor hybrids represent a tantalizing all-electric
alternative. The gatemon is a recently developed transmon variant which employs
locally gated nanowire (NW) superconductor-semiconductor JJs for qubit control.
Here, we go beyond proof-of-concept and demonstrate that semiconducting
channels etched from a wafer-scale two-dimensional electron gas (2DEG) are a
suitable platform for building a scalable gatemon-based quantum computer. We
show 2DEG gatemons meet the requirements by performing voltage-controlled
single qubit rotations and two-qubit swap operations. We measure qubit
coherence times up to ~2 us, limited by dielectric loss in the 2DEG host
substrate
Technologies for trapped-ion quantum information systems
Scaling-up from prototype systems to dense arrays of ions on chip, or vast
networks of ions connected by photonic channels, will require developing
entirely new technologies that combine miniaturized ion trapping systems with
devices to capture, transmit and detect light, while refining how ions are
confined and controlled. Building a cohesive ion system from such diverse parts
involves many challenges, including navigating materials incompatibilities and
undesired coupling between elements. Here, we review our recent efforts to
create scalable ion systems incorporating unconventional materials such as
graphene and indium tin oxide, integrating devices like optical fibers and
mirrors, and exploring alternative ion loading and trapping techniques.Comment: 19 pages, 18 figure
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