6,479 research outputs found
Information and communication in polygon theories
Generalized probabilistic theories (GPT) provide a framework in which one can
formulate physical theories that includes classical and quantum theories, but
also many other alternative theories. In order to compare different GPTs, we
advocate an approach in which one views a state in a GPT as a resource, and
quantifies the cost of interconverting between different such resources. We
illustrate this approach on polygon theories (Janotta et al. New J. Phys 13,
063024, 2011) that interpolate (as the number n of edges of the polygon
increases) between a classical trit (when n=3) and a real quantum bit (when
n=infinity). Our main results are that simulating the transmission of a single
n-gon state requires more than one qubit, or more than log(log(n)) bits, and
that n-gon states with n odd cannot be simulated by n'-gon states with n' even
(for all n,n'). These results are obtained by showing that the classical
capacity of a single n-gon state with n even is 1 bit, whereas it is larger
than 1 bit when n is odd; by showing that transmitting a single n-gon state
with n even violates information causality; and by showing studying the
communication complexity cost of the nondeterministic not equal function using
n-gon states.Comment: 18 page
Anomalous magnetic response of a quasi-periodic mesoscopic ring in presence of Rashba and Dresselhaus spin-orbit interactions
We investigate the properties of persistent charge current driven by magnetic
flux in a quasi-periodic mesoscopic Fibonacci ring with Rashba and Dresselhaus
spin-orbit interactions. Within a tight-binding framework we work out
individual state currents together with net current based on second-quantized
approach. A significant enhancement of current is observed in presence of
spin-orbit coupling and sometimes it becomes orders of magnitude higher
compared to the spin-orbit interaction free Fibonacci ring. We also establish a
scaling relation of persistent current with ring size, associated with the
Fibonacci generation, from which one can directly estimate current for any
arbitrary flux, even in presence of spin-orbit interaction, without doing
numerical simulation. The present analysis indeed gives a unique opportunity of
determining persistent current and has not been discussed so far.Comment: 10 pages, 16 figures (Accepted for Publication in: The European
Physical Journal B-Condensed Matter and Complex Systems
All-spin logic operations: Memory device and Reconfigurable computing
Exploiting spin degree of freedom of electron a new proposal is given to
characterize spin-based logical operations using a quantum interferometer that
can be utilized as a programmable spin logic device (PSLD). The ON and OFF
states of both inputs and outputs are described by {\em spin} state only,
circumventing spin-to-charge conversion at every stage as often used in
conventional devices with the inclusion of extra hardware that can eventually
diminish the efficiency. All possible logic functions can be engineered from a
single device without redesigning the circuit which certainly offers the
opportunities of designing new generation spintronic devices. Moreover we also
discuss the utilization of the present model as a memory device and suitable
computing operations with proposed experimental setups.Comment: 6 pages, 7 figure
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