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• Stimulated Hawking Emission From Electromagnetic Analogue Black Hole: Theory
and Observation, Authors: Avijit Bera, Subir Ghosh, Doi 10.1103/Phys Rev
D.101.105012

(S. Ghosh)

Quantum Foundation and Quantum Information

1. In the context of communication games entanglement and hence nonlocality plays a
fundamental role. But there is interplay between entangled state and measurement in a
entangled basis. There are theories that are highly nonlocal, but do not admit
measurement in entangled basis. Again there may be theories which do not allow
entangled state but incorporate measurement in entangled basis. There are some
computational tasks (distributed computation) where it can be shown that quantum
mechanics provide the best possible solution in terms of limited communications. Other
theories with high nonlocality in state or in measurement, fails in this task. So it seems
that in quantum mechanics there is an optimal compromise between degree of
nonlocality and the degree of measurement in entangled basis in such a way that it
provides optimal advantage in various information processing tasks. It will be
interesting to classify such tasks where QM is superior in terms of advantage when
compared to other hypothetical nonlocal theories.
2. The idea of quantum superposition can be extended to a situation where the relative
order between two events is indefinite. When the events are taken to be quantum gate,
it is called quantum switch. Quantum switch provides advantages in various
communication tasks. Recently it has been shown that use of quantum switch can
provide non-zero classical capacity by making the relative order of two useless channels
indefinite. In this context, we show that two instances of a noisy process, used in a
superposition of two alternative orders, can behave as a perfect quantum
communication channel. This phenomenon occurs even if the original processes have
zero capacity to transmit quantum information. In contrast, perfect quantum
communication does not occur when the message is sent along a superposition of paths,
with independent noise processes acting on each path. The possibility of perfect
quantum communication through noisy channels highlights a fundamental difference
between the superposition of orders in time and the superposition of paths in space.
Further studies of enhanching the quantum and private capacity of useless chanells by
using quantum switch are going on.