Squeezing the limit: Quantum benchmarks for the teleportation and storage of squeezed states

We derive fidelity benchmarks for the quantum storage and teleportation of squeezed states of continuous variable systems, for input ensembles where the degree of squeezing $s$ is fixed, no information about its orientation in phase space is given, and the distribution of phase space displacements is a Gaussian. In the limit where the latter becomes flat, we prove analytically that the maximal classical achievable fidelity (which is 1/2 without squeezing, for $s=1$) is given by $\sqrt{s}/(1+s)$, vanishing when the degree of squeezing diverges. For mixed states, as well as for general distributions of displacements, we reduce the determination of the benchmarks to the solution of a finite-dimensional semidefinite program, which yields accurate, certifiable bounds thanks to a rigorous analysis of the truncation error. This approach may be easily adapted to more general ensembles of input states.Comment: 19 pages, 4figure

Towards a measure of financial fragility

This paper proposes a measure of financial fragility that is based on economic welfare in a general equilibrium model calibrated against UK data. The model comprises a household sector, three active heterogeneous banks, a central bank/regulator, incomplete markets, and endogenous default. We address the impact of monetary and regulatory policy, credit and capital shocks in the real and financial sectors and how the response of the economy to shocks relates to our measure of financial fragility. Finally we use panel VAR techniques to investigate the relationships between the factors that characterise financial fragility in our model, i.e. banks' probabilities of default and banks' profits - to a proxy of welfare