arXiv subjects
Publications and source records attributed to V. L. Gorshenin.
We discuss a new class of pure non-Gaussian quantum states of light characterized by trigonal symmetry on the phase plane. We propose the term ``trigonal states'' for them and show that they can be generated using the standard non-degenerate four-wave process supplemented by the subsequent heralding measurement of the photon number in one of the two signal modes.
We propose to use the antisqueezing-enhanced non-Gaussian Schrödinger cat quantum states of the probing light for the task of detection of a given phase shift in optical interferometers. We show that the antisqueezing allows to increase the robustness of the setup to optical losses. We find the optimal degrees of the antisqueezing for experimentally achievable values of the Schrödinger cat amplitude and the optical losses and compare the resulting sensitivity with the one provided by the Gaussian squeezed states.
The ultimate precision of phase estimation is limited by the Heisenberg scaling $Δϕ_0 = K/N$, where $K\sim1$ is a numerical prefactor and $N$ is the mean number of photons interacting with the phase shifting object(s). However, achieving this fundamental limit often comes at the cost of an extremely narrow high-sensitive range, rendering schemes impractical. We analyze the precision limits of phase measurements in single- and two-arm optical interferometers with input Gaussian states. We consider two detection methods: conventional homodyne measurement and non-Gaussian threshold detection that saturates the quantum Cramér-Rao bound. We characterize the performance by two complementary metrics: the peak sensitivity $Δϕ_0$ and the width $δϕ$ of the high-sensitivity range. We demonstrate that Heisenberg scaling is attainable in all configurations considered. However, we reveal that $δϕ$ strongly depends on $K$. We derive an approximate analytic expression that describes this trade-off. We show also that the two-arm interferometer with antisymmetrically squeezed inputs exhibits exceptional performance, simultaneously achieving Heisenberg-limited sensitivity and a broad high-sensitivity range $δϕ=π/2$.
Schrödinger-cat (SC) states are an important resource for continuous-variable quantum computing and quantum metrology. In our previous work [JOSA B, 42, 2 (2025)], we proposed a probabilistic protocol for generating bright squeezed SC states via degenerate spontaneous parametric down-conversion (SPDC) with pump depletion, followed by projective measurement of the pump mode. In the present work, we formulate a general theoretical description of SPDC with pump depletion, introduce an efficient numerical method for computing its dynamics, and develop a practical version of the protocol proposed in [JOSA B, 42, 2 (2025)].
The Schrödinger cat (SC) states are important in quantum optics because of their non-Gaussian properties. We propose a novel method of conditional generation of bright (multi-photon) SC states that uses degenerate parametric down-conversion and heralding measurement of the photon number in the pump mode. We show that this method, in principle, could be implemented using the modern high-\(Q\) optical microresonators.
We show that injecting a light pulse prepared in the Shroedinger cat quantum state into the dark port of a two-arm interferometer and the strong classical light into the bright one, it is possible, in principle, to detect a given phase shift unambiguously. The value of this phase shift is inversely proportional to the amplitudes of both the classical carrier and Shroedinger cat state. However, an exotic detection procedure is required for this purpose. By measuring the number of photons at the output dark port, it is possible to detect the phase shift with the vanishing "false positive" probability. The "false negative" probability in this case decreases with the increase on the amplitude of the Schroedinger cat state and, for reasonable values of this amplitude, can be made as small as about 0.1.
Injecting a non-Gaussian (Fock or Shrödinger cat) quantum state into the dark port of a two-arm interferometer and a strong classical light into the bright one, it is possible, in principle, to detect a given phase shift unambiguously using the orthogonality between the original and displaced in the interferometer non-Gaussian states. The optical losses degrade the sensitivity, introducing the finite "false positive" and "false negative" detection errors. However, using the state-of-art photodetectors, it is still possible to obtain better detection fidelity than in the case of Gaussian quantum states.