Quantum measurements of atoms using cavity QED

Abstract

Generalized quantum measurements are an important extension of projective or von Neumann measurements, in that they can be used to describe any measurement that can be implemented on a quantum system. We describe how to realize two non-standard quantum measurements using cavity quantum electrodynamics (QED). The first measurement optimally and unabmiguously distinguishes between two non-orthogonal quantum states. The second example is a measurement that demonstrates superadditive quantum coding gain. The experimental tools used are single-atom unitary operations effected by Ramsey pulses and two-atom Tavis-Cummings interactions. We show how the superadditive quantum coding gain is affected by errors in the field-ionisation detection of atoms, and that even with rather high levels of experimental imperfections, a reasonable amount of superadditivity can still be seen. To date, these types of measurement have only been realized on photons. It would be of great interest to have realizations using other physical systems. This is for fundamental reasons, but also since quantum coding gain in general increases with code word length, and a realization using atoms could be more easily scaled than existing realizations using photons.Comment: 10 pages, 5 figure

Relativistic motion enhanced quantum estimation of $$\kappa $$ κ -deformation of spacetime

“…It indicates that the estimation of deformation parameter κ via the population measurement is optimal and we can get the ultimate bound to precision of estimation. Due to the population measurement is optimal and the population of estimation measurement is allowed by the current technology [80][81][82][83][84][85][86], the ultimate bound to precision of estimation of the deformation parameter κ can be achieved by quantum mechanics in the capability of current technology for the optimal population measurement.…”

Measurement-induced chaos and quantum state discrimination in an iterated Tavis-Cummings scheme

“…Recently, it has been demonstrated [13] that the resulting strong sensitivity to initial conditions can, in principle, be used to amplify small initial differences of quantum states, thus realizing a Schrödinger microscope, a term originally suggested by Lloyd and Slotine [14], capable of distinguishing nonorthogonal quantum states. Although Helstrom and Ivanov-Dieks-Peres measurements have already been realized experimentally both optically [15,16] and in the solid state [17], a Schrödinger microscope based on nonlinear quantum state transformations has not yet been realized.…”

Optimal minimum-cost quantum measurements for imperfect detection

“…For example, for a measurement on an atom or ion, we may couple the levels of the atom or ion to some additional atomic levels e.g. using laser pulses or passage through a cavity [15,17], followed by a final measurement of which energy level the atom or ion occupies. Due to experimental constraints, the final measurement is restricted to be a projection in the energy eigenbasis.…”

“…[6][7][8][9][10][11][12][13], and very recently on NV-centres in diamond [14]. They could also be realized on ions or atoms with existing experimental tools [15][16][17].…”