163 research outputs found
Quantum Memristors in Quantum Photonics
We propose a method to build quantum memristors in quantum photonic
platforms. We firstly design an effective beam splitter, which is tunable in
real-time, by means of a Mach-Zehnder-type array with two equal 50:50 beam
splitters and a tunable retarder, which allows us to control its reflectivity.
Then, we show that this tunable beam splitter, when equipped with weak
measurements and classical feedback, behaves as a quantum memristor. Indeed, in
order to prove its quantumness, we show how to codify quantum information in
the coherent beams. Moreover, we estimate the memory capability of the quantum
memristor. Finally, we show the feasibility of the proposed setup in integrated
quantum photonics
Energy efficient mining on a quantum-enabled blockchain using light
We outline a quantum-enabled blockchain architecture based on a consortium of
quantum servers. The network is hybridised, utilising digital systems for
sharing and processing classical information combined with a fibre--optic
infrastructure and quantum devices for transmitting and processing quantum
information. We deliver an energy efficient interactive mining protocol enacted
between clients and servers which uses quantum information encoded in light and
removes the need for trust in network infrastructure. Instead, clients on the
network need only trust the transparent network code, and that their devices
adhere to the rules of quantum physics. To demonstrate the energy efficiency of
the mining protocol, we elaborate upon the results of two previous experiments
(one performed over 1km of optical fibre) as applied to this work. Finally, we
address some key vulnerabilities, explore open questions, and observe
forward--compatibility with the quantum internet and quantum computing
technologies.Comment: 25 pages, 5 figure
Entanglement Capacity of Nonlocal Hamiltonians : A Geometric Approach
We develop a geometric approach to quantify the capability of creating
entanglement for a general physical interaction acting on two qubits. We use
the entanglement measure proposed by us for -qubit pure states (PRA
\textbf{77}, 062334 (2008)). Our procedure reproduces the earlier results (PRL
\textbf{87}, 137901 (2001)). The geometric method has the distinct advantage
that it gives an experimental way to monitor the process of optimizing
entanglement production.Comment: 8 pages, 1 figure
Are Electrons Oscillating Photons, Oscillating “Vacuum," or Something Else? The 2015 Panel Discussion: An Unprecedented Engineering Opportunity: A Dynamical Linear Theory of Energy as Light and Matter
Platform: What physical attributes separate EM waves, of the enormous band of radio to visible to x-ray, from the high energy narrow band of gamma-ray? From radio to visible to x-ray, telescopes are designed based upon the optical imaging theory; which is an extension of the Huygens-Fresnel diffraction integral. Do we understand the physical properties of gamma rays that defy us to manipulate them similarly? One demonstrated unique property of gamma rays is that they can be converted to elementary particles (electron and positron pair); or a particle-antiparticle pair can be converted into gamma rays. Thus, EM waves and elementary particles, being inter-convertible; we cannot expect to understand the deeper nature of light without succeeding to find structural inter-relationship between photons and particles. This topic is directly relevant to develop a deeper understanding of the nature of light; which will, in turn, help our engineers to invent better optical instruments
Information Theoretic Resources in Quantum Theory
Resource identification and quantification is an essential element of both
classical and quantum information theory. Entanglement is one of these
resources, arising when quantum communication and nonlocal operations are
expensive to perform. In the first part of this thesis we quantify the
effective entanglement when operations are additionally restricted. For an
important class of errors we find a linear relationship between the usual and
effective higher dimensional generalization of concurrence, a measure of
entanglement.
In the second chapter we focus on nonlocality in the presence of
superselection rules, where we propose a scheme that may be used to activate
nongenuinely multipartite nonlocality with multiple copies of the state. We
show that whenever the number of particles is insufficient, the genuinely
multipartite nonlocality is degraded to nongenuinely multipartite.
While in the first few chapters we focus on understanding the resources
present in quantum states, in the final part we turn the picture around and
instead treat operations themselves as a resource. We provide our observers
with free access to classical operations - ie. those that cannot detect or
generate quantum coherence. We show that the operation of interest can then be
used to either generate or detect quantum coherence if and only if it violates
a particular commutation relation. Using the relative entropy, the commutation
relation provides us with a measure of nonclassicality of operations. We show
that the measure is a sum of two contributions, the generating power and the
distinguishing power, each of which is separately an essential ingredient in
quantum communication and information processing. The measure also sheds light
on the operational meaning of quantum discord, which we show can be interpreted
as the difference in superdense coding capacity between a quantum state and a
classical state.Comment: Thesis, 109 page
- …