The fundamental properties of light derive from its constituent particles—massless quanta
(photons) that do not interact with one another. However, it has long been known that the …

We present a scalable method for the tomography of large multiqubit quantum registers. It
acquires information about the permutationally invariant part of the density operator, which is …

Quantum interference of two independent particles in pure quantum states is fully described
by the particles' distinguishability: the closer the particles are to being identical, the higher …

When used in quantum state estimation, projections onto mutually unbiased bases have the
ability to maximize information extraction per measurement and to minimize redundancy. We …

Quantum metrology uses entanglement,,, and other quantum effects to improve the
sensitivity of demanding measurements,,. Probing of delicate systems demands high …

Realizing a strong interaction between individual photons is an important objective of
research in quantum science and technology. It requires an optical medium in which light …

Quantum phenomena present in many experiments signify nonclassical behavior, but do not
always imply superior performance. Quantifying the enhancement achieved from quantum …

Feasible tomography schemes for large particle numbers must possess, besides an
appropriate data acquisition protocol, an efficient way to reconstruct the density operator …

It is often thought that the super-sensitivity of a quantum state to an observable comes at the
cost of a decreased sensitivity to other non-commuting observables. For example, a …

We have performed experimental quantum state tomography of NOON states with up to four
photons. The measured states are generated by mixing photons from a classical coherent …