Hi all,
This week Alastair Abbott is visiting from Geneva. Tomorrow he'll tell us
about "Quantum Circuits with Classical and Quantum Control of Causal
Orders". See below for the abstract.
Best,
-joe
Abstract:
The standard approach to quantum information processing, including the
quantum circuit framework, implicitly assumes that operations are applied
in a well defined causal order. However, quantum mechanics allows the order
in which operations are applied to itself be in a quantum superposition.
This observation has led to the process matrix formalism describing quantum
processes without any global causal order.
I will review a simple such process, the "quantum switch", that enables
several advantages in quantum information. In fact, the quantum switch and
its generalisation are thus far the only known "causally indefinite"
processes for which a physical implementation is known to be possible. With
this motivation, I will present two generalisations of standard quantum
circuits: quantum circuits with classical and quantum control of causal
order. These can be nicely characterised and the latter provides a concrete
way of pursuing new noncausal processes that are, by construction,
physically implementable.