3,650 research outputs found
III-V-on-silicon photonic devices for optical communication and sensing
In the paper, we review our work on heterogeneous III-V-on-silicon photonic components and circuits for applications in optical communication and sensing. We elaborate on the integration strategy and describe a broad range of devices realized on this platform covering a wavelength range from 850 nm to 3.85 ÎŒm
From Low-Distortion Norm Embeddings to Explicit Uncertainty Relations and Efficient Information Locking
The existence of quantum uncertainty relations is the essential reason that
some classically impossible cryptographic primitives become possible when
quantum communication is allowed. One direct operational manifestation of these
uncertainty relations is a purely quantum effect referred to as information
locking. A locking scheme can be viewed as a cryptographic protocol in which a
uniformly random n-bit message is encoded in a quantum system using a classical
key of size much smaller than n. Without the key, no measurement of this
quantum state can extract more than a negligible amount of information about
the message, in which case the message is said to be "locked". Furthermore,
knowing the key, it is possible to recover, that is "unlock", the message. In
this paper, we make the following contributions by exploiting a connection
between uncertainty relations and low-distortion embeddings of L2 into L1. We
introduce the notion of metric uncertainty relations and connect it to
low-distortion embeddings of L2 into L1. A metric uncertainty relation also
implies an entropic uncertainty relation. We prove that random bases satisfy
uncertainty relations with a stronger definition and better parameters than
previously known. Our proof is also considerably simpler than earlier proofs.
We apply this result to show the existence of locking schemes with key size
independent of the message length. We give efficient constructions of metric
uncertainty relations. The bases defining these metric uncertainty relations
are computable by quantum circuits of almost linear size. This leads to the
first explicit construction of a strong information locking scheme. Moreover,
we present a locking scheme that is close to being implementable with current
technology. We apply our metric uncertainty relations to exhibit communication
protocols that perform quantum equality testing.Comment: 60 pages, 5 figures. v4: published versio
Recent developments in monolithic integration of InGaAsP/InP optoelectronic devices
Monolithically integrated optoelectronic circuits combine optical devices such as light sources (injection lasers and light emitting diodes) and optical detectors with solid-state semiconductor devices such as field effect transistors, bipolar transistors, and others on a single semiconductor crystal. Here we review some of the integrated circuits that have been realized and discuss the laser structures suited for integration with emphasis on the InGaAsP/InP material system. Some results of high frequency modulation and performance of integrated devices are discussed
Breadboard model of the LISA phasemeter
An elegant breadboard model of the LISA phasemeter is currently under
development by a Danish-German consortium. The breadboard is build in the frame
of an ESA technology development activity to demonstrate the feasibility and
readiness of the LISA metrology baseline architecture. This article gives an
overview about the breadboard design and its components, including the
distribution of key functionalities.Comment: 5 pages, 3 figures, published in ASP Conference Series, Vol. 467, 9th
LISA Symposium (2012), pp 271-27
Matrix multiplication using quantum-dot cellular automata to implement conventional microelectronics
Quantum-dot cellular automata (QCA) shows promise as a post silicon CMOS, low
power computational technology. Nevertheless, to generalize QCA for
next-generation digital devices, the ability to implement conventional
programmable circuits based on NOR, AND, and OR gates is necessary. To this
end, we devise a new QCA structure, the QCA matrix multiplier (MM), employing
the standard Coulomb blocked, five quantum dot (QD) QCA cell and
quasi-adiabatic switching for sequential data latching in the QCA cells. Our
structure can multiply two N x M matrices, using one input and one
bidirectional input/output data line. The calculation is highly parallelizable,
and it is possible to achieve reduced calculation time in exchange for
increasing numbers of parallel matrix multiplier units. We show convergent, ab
initio simulation results using the Intercellular Hartree Approximation for
one, three, and nine matrix multiplier units. The structure can generally
implement any programmable logic array (PLA) or any matrix multiplication based
operation.Comment: 14 pages, 9 figures, supplemental informatio
Voltage-Current curves for small Josephson junction arrays
We compute the current voltage characteristic of a chain of identical
Josephson circuits characterized by a large ratio of Josephson to charging
energy that are envisioned as the implementation of topologically protected
qubits. We show that in the limit of small coupling to the environment it
exhibits a non-monotonous behavior with a maximum voltage followed by a
parametrically large region where . We argue that its
experimental measurement provides a direct probe of the amplitude of the
quantum transitions in constituting Josephson circuits and thus allows their
full characterization.Comment: 12 pages, 4 figure
- âŠ