Talk @UFRJ, Paul Boes, Monday 03/12, 15H30Posted: November 28, 2018
The Quantum Optics and Information Group (UFRJ) is proud to announce last seminar of the year, which will be given by Paul Boes (Freie Universitat Berlin). We invite all to come!
See the details of the talk below:
MONDAY, December 3rd, at 15H30
in room 343 (3rd floor of block A of the Technology Center building)
“Catalytic Quantum Randomness”
Paul Boes (Freie Universitat Berlin)
Randomness is a defining element of mixing processes in nature and an essential ingredient to many protocols in quantum information. In this talk, we investigate how much randomness is required to transform a given quantum state into another one. Specifically, we ask whether there is a gap between the power of a classical source of randomness compared to that of a quantum one. We provide a complete answer to these questions, by identifying provably optimal protocols for both classical and quantum sources of randomness, based on a dephasing construction. We find that in order to implement any noisy transition on a d-dimensional quantum system it is necessary and sufficient to have a quantum source of randomness of dimension \sqrt(d) or a classical one of dimension d. Interestingly, coherences provided by quantum states in a source of randomness offer a quadratic advantage. The process we construct has the additional features to be robust and catalytic, i.e., the source of randomness can be re-used. Building upon this formal framework, we illustrate that this dephasing construction can serve as a useful primitive in both equilibration and quantum information theory: We discuss applications describing the smallest measurement device, capturing the smallest equilibrating environment allowed by quantum mechanics, or forming the basis for a cryptographic private quantum channel. Starting with the catalytic nature of the source of randomness, we also discuss more generally the usefulness of correlated catalysts. In this context, we present a conjecture – that the possible state transitions that can be implemented with correlated catalysts are characterised by the von Neumann entropy – and present some evidence of this conjecture.
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