The previous meeting was held on Wednesday 15th December
in the Gavin de Beer Lecture Theatre
in the Anatomy Building of University College London.
"The power of quantum correlations in physics and computation"
Janet Anders (UCL)
Quantum correlations, i.e. entanglement, appears in many natural and
experimental physical situations and is an ingredient in quantum
computation. Their appearance marks the establishment of a
qualitatively different behaviour - be it a new phase, such as a BEC,
or a resource for impossible computations. I will give an overview of
a range of contexts where entanglement plays such a role. Finally, I
will discuss claims that quantum correlations lead to a violation of
the second law of thermodynamics and with it Landauer's erasure
principle. I will argue why these claims are erroneous and show how a
consistent treatment of correlations in this thermodynamical context
resolves the paradoxical situation.
"Quantum accelerometer: distinguishing inertial Bob from his
accelerated twin Rob by a local measurement"
Andrzej Dragan (Warsaw)
A single point-like detector can be used to determine absolute
acceleration by local measurements on a quantum field. To show this,
we consider two kinematically indistinguishable scenarios: an
inertial observer, Bob, measuring the field of an uniformly
accelerated cavity, and his non-inertial twin Rob accelerating and
making measurements in a stationary cavity. We find that these
scenarios can be distinguished in the non-relativistic regime only by
measurements on highly excited massive fields, allowing one to detect
non-inertialness of the reference frame.
"How much "free choice" is needed in order to demonstrate nonlocality?"
Jonathan Barrett (Royal Holloway)
If nonlocality is to be inferred from a violation of a Bell
inequality, an important assumption is that the measurement settings are
freely chosen by the observers, or alternatively, that they are random
and uncorrelated with the hypothetical local variables. I will examine
the case where this assumption is weakened, so that measurement settings
and local variables are at least partially correlated. It turns out that
there is a connection between this type of model and models which
reproduce nonlocal correlations by allowing classical communication
between the distant parties. Exploiting this connection, I show that,
with Bob's choice completely independent, if the correlation between
Alice's choice and the local variables is just a single bit (of mutual
information), then all correlations obtained from projective
measurements on a singlet can be reproduced by local means.
"Quantum Dynamical Probing of Community Structure in Complex Networks"
Dimitris Tsomokos (Royal Holloway)
Complex networks are structurally disordered systems that often display
clustering behavior. The emergent clusters, also known as communities,
consist of nodes that are more connected among themselves than they are
connected with the rest of the network. Analyzing community structure is an
important problem in network theory, with numerous applications in different
fields. In this talk I explain how the evolution of a continuous-time
quantum random walk on a complex network can be used to perform community
"Singlet-Triplet Measurement through Coherent Evolution of a Single
Abolfazl Bayat (UCL)
A proposal for singlet-triplet spin measurement is introduced through
exploiting the non-dissipative dynamics of a pair of electrons in a large
square quantum dot followed by a single charge detection. It is shown that
this may be used for entanglement swapping and teleportation. The method
is also used to generate the AKLT ground state, a further resource for
quantum computation. We justify, and derive analytic results for, an
effective charge-spin Hamiltonian which is valid over a wide range of
parameters and agrees well with exact numerical results of a realistic
effective-mass model. Our analysis also indicates that the method is
robust to choice of dot-size and initialization errors, as well as
decoherence introduced by the hyperfine interaction.
"What is the laziest way of doing Quantum
Daniel Burgarth (Imperial)