Quantum non-Gaussianity of multi-phonon states of a single atom

Abstract

Quantum non-Gaussian mechanical states from inherently nonlinear quantum processes are already required in a range of applications spanning from quantum sensing up to quantum computing with continuous variables. The discrete building blocks of such states are the energy eigenstates -Fock states. Despite the progress in their preparation, the remaining imperfections can still invisibly cause loss of the critical quantum non-Gaussian aspects of the phonon distribution relevant in the applications. We derive the most challenging hierarchy of quantum non-Gaussian criteria for the individual mechanical Fock states and demonstrate its implementation on the characterization of single trapped-ion oscillator states up to 10 phonons. We analyze the depth of quantum non-Gaussian features under mechanical heating and predict their application in quantum sensing. These results uncover that the crucial quantum non-Gaussian features are demanded to reach quantum advantage in the applications.

Single-mode Quantum Non-Gaussian Light from Warm Atoms

“…This corresponds to the relative fluctuation of the mutual spatial alignment of two fiber-coupled detection of 6 %, which accounts for a visible shift between the set of green data and the corresponding orange data point at d = −1.9 cm with no excess thermal noise. We remind that, besides the crucial role of estimation of QNG depth as general and robust comparison of quality of QNG sources with extensions beyond the optical domain [64], it can be also employed for estimation of tolerance of generated QNG properties against intrinsic noise sources and provide a means for an unambiguous optimization of source parameters.…”

Swap-test interferometry with biased ancilla noise

“…In trappedion and superconducting systems, where the controlledswap gates are readily available [34,36,39], interferometry with NOON states becomes much more straightforward: a NOON state can be both prepared and measured in a single step irrespective of its size. The only resource needed is then an input Fock state |n , for which efficient preparation methods exist in both circuit QED [41][42][43] and trapped-ion systems [44,45].…”