2 research outputs found
Entanglement in mutually unbiased bases
One of the essential features of quantum mechanics is that most pairs of
observables cannot be measured simultaneously. This phenomenon is most strongly
manifested when observables are related to mutually unbiased bases. In this
paper, we shed some light on the connection between mutually unbiased bases and
another essential feature of quantum mechanics, quantum entanglement. It is
shown that a complete set of mutually unbiased bases of a bipartite system
contains a fixed amount of entanglement, independently of the choice of the
set. This has implications for entanglement distribution among the states of a
complete set. In prime-squared dimensions we present an explicit
experiment-friendly construction of a complete set with a particularly simple
entanglement distribution. Finally, we describe basic properties of mutually
unbiased bases composed only of product states. The constructions are
illustrated with explicit examples in low dimensions. We believe that
properties of entanglement in mutually unbiased bases might be one of the
ingredients to be taken into account to settle the question of the existence of
complete sets. We also expect that they will be relevant to applications of
bases in the experimental realization of quantum protocols in
higher-dimensional Hilbert spaces.Comment: 13 pages + appendices. Published versio
Integrated Photonic Sensing
Loss is a critical roadblock to achieving photonic quantum-enhanced
technologies. We explore a modular platform for implementing integrated
photonics experiments and consider the effects of loss at different stages of
these experiments, including state preparation, manipulation and measurement.
We frame our discussion mainly in the context of quantum sensing and focus
particularly on the use of loss-tolerant Holland-Burnett states for optical
phase estimation. In particular, we discuss spontaneous four-wave mixing in
standard birefringent fibre as a source of pure, heralded single photons and
present methods of optimising such sources. We also outline a route to
programmable circuits which allow the control of photonic interactions even in
the presence of fabrication imperfections and describe a ratiometric
characterisation method for beam splitters which allows the characterisation of
complex circuits without the need for full process tomography. Finally, we
present a framework for performing state tomography on heralded states using
lossy measurement devices. This is motivated by a calculation of the effects of
fabrication imperfections on precision measurement using Holland-Burnett
states.Comment: 19 pages, 7 figure