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SPIE Quantum Technologies

Guided-wave solutions for non-classical state production

Mohamed Faouzi Melalkia, Tecla Gabbrielli, Antoine Petitjean, Alessandro Zavatta, F. Brunel, Sébastien Tanzilli, Jean Etesse, Virginia D’Auria

Published May 31, 2022• 2 citations
Publisher

Abstract

We demonstrate the possibility of generating non-Gaussian states of light by exploiting a setup fully based on plug-and-play guided-wave components from classical telecom and non-linear optical technologies. Our scheme relies on heralded single photon subtraction from single mode squeezed states generated in a single-pass configuration in nonlinear optical waveguides and allows generating Schrodinger kitten quantum optical states. We discuss the different parameters affecting the shape of obtained states by comparing the theory and the numerical simulations.

DOI
10.1117/12.2631333

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Journal of Visualized Experiments•May 30, 2014•7 citations
We demonstrate the possibility of generating non-Gaussian states of light by exploiting a setup fully based on plug-and-play guided-wave components from classical telecom and non-linear optical technologies. Our scheme relies on heralded single photon subtraction from single mode squeezed states generated in a single-pass configuration in nonlinear optical waveguides and allows generating Schrodinger kitten quantum optical states. We discuss the different parameters affecting the shape of obtained states by comparing the theory and the numerical simulations.
In the context of emerging quantum technologies, this work marks an important progress towards practical quantum optical systems in the continuous variable regime. It shows the feasibility of experiments where non-Gaussian state generation entirely relies on plug-and-play components from guided-wave optics technologies. This strategy is successfully demonstrated with the heralded preparation of low amplitude Schrödinger cat states via single-photon subtraction from a squeezed vacuum. All stages of the experiment are based on off-the-shelf fiber components. This leads to a stable, compact, and easily re-configurable realization, fully compatible with existing fiber networks and, more in general, with future out-of-the-laboratory applications.
We demonstrate, for the first time, the realization of an entirely guided-wave squeezing experiment at a telecom wavelength. The state generation relies on waveguide non-linear optics technology while squeezing collection and transmission are implemented by using only telecom fibre components. We observe up to −1.83±0.05-1.83\pm0.05−1.83±0.05 dB of squeezing emitted at 1542 nm in CW pumping regime. The compactness and stability of the experiment, compared to free-space configurations, represent a significant step towards achieving out-of-the-lab CV quantum communication, fully compatible with existing telecom fibre networks. We believe that this work stands as a promising approach for real applications as well as for "do-it-yourself" experiments
In this work, we study the generation of non-Gaussian quantum states of light using multimode quantum resources. We first propose a theoretical framework to describe photon subtraction operation - a well known non-Gaussian operation - applied to a multimode Gaussian state. We apply this framework to the case of Schrödinger kitten state generation using a multimode squeezed vacuum as input state. We show that a monomode non-Gaussian state with high purity can be generated by a better choice of the different experimental parameters. Then, we propose a new protocol to generate high amplitude non-Gaussian states using spectral multiplexing of input states and Gaussian operations. We show that this protocol can implement the cat breeding operation with less complexity. We show also that this protocol can be used for the generation of approximated GKP state.
Continuous-variable quantum computing exploits the modes of electromagnetic fields to encode information. Multiplexing generates massive entangled states, called cluster states. These structures support measurement-based quantum computing. Purely Gaussian operations restrict computational power. The Gottesman-Knill theorem demonstrates that a classical algorithm efficiently simulates a Gaussian optical circuit. Quantum advantage requires the introduction of non-Gaussian processes. The generation of Schrödinger kitten states answers this need. These non-classical states authorize the realization of non-linear logic gates. They provide the fundamental resources for Gottesman-Kitaev-Preskill (GKP) error correction codes. The production of these resources constitutes a physical problem. Pure states undergo rapid decoherence under the effect of optical losses. Attenuation alters the quantum properties. The Wigner function loses its negativity. The state degenerates into a statistical mixture. Until now, experiments used free-space components. These macroscopic configurations present a restrictive mechanical instability. These limits oppose the miniaturization required by modern quantum processors. Tomography requires electronic acquisition chains with very high bandwidth. These technological barriers completely prevent the physical scaling of computation architectures. This manuscript describes the development of guided-wave non-Gaussian state generators. The experimental system operates at the telecommunications wavelength (1560 nm). A continuous-wave laser precisely pumps periodically poled lithium niobate (PPLN) waveguides. These crystalline structures generate squeezed vacuum states. A fiber coupler extracts a minimal fraction of the beam. A Fabry-Pérot cavity filters this spatial mode. A superconducting nanowire single-photon detector (SNSPD) signals the arrival of a single photon. This exact detection heralds the subtraction of a photon from the main optical mode. The operation projects the system into a non-Gaussian state. The architecture is entirely fiber-integrated to minimize physical losses. The setup integrates a distribution protocol over two distant nodes. An active feedback system stabilizes the optical interferometers. The control uses a counter-propagating probe, frequency-shifted by 2.7 GHz. Experimental measurements validate this architecture. The device generated Schrödinger kitten states. Homodyne tomographic reconstruction confirms the non-Gaussian nature of the resource. The experiment measures a negative value of the Wigner function, W(0,0) = -0,085. A numerical study evaluates the criteria for quantum tomography. The simulations directly connect the electronic detection bandwidth to the physical preservation of negativity. Strict compliance with the Nyquist-Shannon theorem prevents the spectral aliasing of quantum noise. The detector bandwidth must exceed five times the cavity linewidth. The setup tested the creation of distant non-Gaussian entangled states. The protocol exploits the temporal erasure of path information. The filtering cavity elongates the wave packet and suppresses the distinguishability due to fiber asymmetry. The use of guided waves eliminates the instabilities of non-Gaussian sources. Photon subtraction provides a generation method compatible with fiber networks. This work validates the experimental production of highly sensitive quantum states. These results constitute a solid hardware basis for designing optical processors. The transposition to lithium niobate on insulator (LNOI) integrated photonics will allow the development of continuous-variable quantum computers.
Entangled photons are pivotal elements in emerging quantum information technologies. While several schemes are available for the production of entangled photons, they typically require the assistance of cumbersome optical elements to couple them to other components involved in logic operations. Here, we introduce a scheme by which entangled photon pairs are directly generated as guided mode states in optical waveguides. The scheme relies on the intrinsic nonlinearity of the waveguide material, circumventing the use of bulky optical components and their associated phase-matching constraints. Specifically, we consider an optical waveguide under normal illumination, so that photon down-conversion can take place to excite waveguide states with opposite momentum in a spectral region populated by only two accessible modes. By additionally configuring the external illumination to interfere different incident directions, we can produce maximally entangled photon-pair states, directly generated as waveguide modes with conversion efficiencies that are competitive with respect to existing macroscopic schemes. These results should find application in the design of more efficient and compact quantum optics devices.
Engineering non-classical states of the electromagnetic field is a central quest for quantum optics1,2. Beyond their fundamental significance, such states are indeed the resources for implementing various protocols, ranging from enhanced metrology to quantum communication and computing. A variety of devices can be used to generate non-classical states, such as single emitters, light-matter interfaces or non-linear systems3. We focus here on the use of a continuous-wave optical parametric oscillator3,4. This system is based on a non-linear χ2 crystal inserted inside an optical cavity and it is now well-known as a very efficient source of non-classical light, such as single-mode or two-mode squeezed vacuum depending on the crystal phase matching. Squeezed vacuum is a Gaussian state as its quadrature distributions follow a Gaussian statistics. However, it has been shown that number of protocols require non-Gaussian states5. Generating directly such states is a difficult task and would require strong χ3 non-linearities. Another procedure, probabilistic but heralded, consists in using a measurement-induced non-linearity via a conditional preparation technique operated on Gaussian states. Here, we detail this generation protocol for two non-Gaussian states, the single-photon state and a superposition of coherent states, using two differently phase-matched parametric oscillators as primary resources. This technique enables achievement of a high fidelity with the targeted state and generation of the state in a well-controlled spatiotemporal mode.