Optical Synthesis of Large-Amplitude Squeezed Coherent-State Superpositions with Minimal Resources

Abstract

We propose and experimentally realize a novel versatile protocol that allows the quantum state engineering of heralded optical coherent-state superpositions. This scheme relies on a two-mode squeezed state, linear mixing and a n-photon detection. It is optimally using expensive non-Gaussian resources to build up only the key non-Gaussian part of the targeted state. In the experimental case of a two-photon detection based on high-efficiency superconducting nanowire single-photon detectors, the freely propagating state exhibits a 67% fidelity with a squeezed even coherent-state superposition with a size |α| 2 =3. The demonstrated procedure and the achieved rate will facilitate the use of such superpositions in subsequent protocols, including fundamental tests and optical hybrid quantum information implementations.

Efficient Optical Generation of Large-Amplitude Schrödinger Cat States with Minimal Resources

“…The generated state exhibits the highest amplitude and fidelity reported to date for free-propagating CSS, and importantly a preparation rate about 200 Hz is achieved, as we recently reported in [3]. These observations are made possible by implementing a strategy focusing all the non-Gaussian resources to prepare only the non-Gaussian part of the state, and by the combination of a large escape efficiency optical parametric oscillator and high-efficiency superconducting nanowire single-photon detectors.…”

Local versus global strategies in multiparameter estimation

“…For example, local strategies have greater flexibility in the distribution of resources and are more robust to local estimation failure. Furthermore, single-mode states with a large number variance can be made in experiments [14][15][16][17], and realistic schemes have been proposed to produce separable states that improve over the shot-noise limit by more than a factor of 4 [18]. By comparison, multimode-entangled states with large photon numbers are notoriously difficult to make: the largest two-mode optical NOON state that has been made experimentally contains only five photons [27].…”

“…In this more general setting we demonstrate that the same precision enhancements exhibited by the global strategies can be obtained with mode-separable states and local measurements alone. Local strategies offer a number of advantages over their global counterparts, including robustness to local estimation failure, more flexibility in the distribution of resources, and more realistic methods of state preparation [14][15][16][17][18], measurement, and control.…”

Synthesis of Hermite polynomial excited squeezed vacuum states from two separate single-mode squeezed vacuum states

“…In fact, the HPESVS under our consideration is an ideal nonclassical quantum state with general form. Very recently, Huang et al [41] proposed and experimentally realized such a versatile protocol that allows the quantum state engineering of heralded optical coherent-state superpositions, which is used as fundamental tests and optical hybrid quantum information implementations. Interestingly, our theoretical model is an extended work of their scheme.…”