A squeezed state is a key quantum resource for quantum information processing and quantum metrology. It is essential to extend the dimension of the squeezed state for spatially multiplexed large-capacity quantum communication and quantum precision measurements. Here, we report the experimental preparation of a picosecond pulsed squeezed state carrying orbital angular momentum (OAM). By modulating bright pulsed squeezed light with a spatial light modulator, we generate a squeezed state with Laguerre-Gaussian distribution, whose topological charges are up to l = 20 and squeezed noise is 1.22 dB below the shot noise level. The presented bright picosecond pulsed squeezed light carrying high-order OAM provides promising resources for high-dimensional quantum information processing.
A squeezed state is a key quantum resource for quantum information processing and quantum metrology. It is essential to extend the dimension of the squeezed state for spatially multiplexed large-capacity quantum communication and quantum precision measurements. Here, we report the experimental preparation of a picosecond pulsed squeezed state carrying orbital angular momentum (OAM). By modulating bright pulsed squeezed light with a spatial light modulator, we generate a squeezed state with Laguerre-Gaussian distribution, whose topological charges are up to l = 20 and squeezed noise is 1.22 dB below the shot noise level. The presented bright picosecond pulsed squeezed light carrying high-order OAM provides promising resources for high-dimensional quantum information processing.
Abstract As an important quantum resource, optical cat state is successfully prepared and applied in quantum information science. It is shown that optical quantum states carrying orbital angular momentum (OAM) have wide applications in quantum communication and quantum precision measurement. Here, optical cat states carrying OAM are experimentally prepared with topological charges = 0, +1, +2, +4 by changing the wavefront of the photon‐subtracted squeezed vacuum state with a combination of quarter‐wave plate and q‐plate. To verify the prepared cat states, both Wigner functions and topological charges of OAM are measured. It is shown that the fidelities and amplitudes of optical cat states carrying OAM decrease slightly with the increase of topological charges of OAM, although the spatial size of the optical beam is increased. These results present a new kind of optical cat state carrying OAM, which has potential applications in quantum precision measurement.
Spatially structured quantum states, such as orbital angular momentum (OAM) squeezing and entanglement, is currently a popular topic in quantum optics. The method of generating and manipulating spatial quantum states on demand needs to be explored. In this paper, we generated OAM mode squeezed states of −5.4 dB for the L G 0 + 1 mode and −5.3 dB for the L G 0 − 1 mode directly by an optical parametric oscillator (OPO) for the first time. Additionally, we demonstrated that the OAM mode squeezed and entangled states were respectively generated by manipulating the nonlinear process of the OPO by controlling the relative phase of two beams of different modes, thus making two different spatial multimode pump beams. We characterized the Laguerre-Gaussian (LG) entangled states by indirectly measuring the squeezing for the H G 10 ( 45 ∘ ) mode and H G 10 ( 135 ∘ ) mode, and directly measuring the entanglement between the L G 0 + 1 and L G 0 − 1 modes. The effective manipulation of the OAM quantum state provides a novel insight into the continuous variable quantum state generation and construction on demand for high-dimensional quantum information and quantum metrology.
ABSTRACT Broadband bright squeezed states are important quantum resources that play a crucial role in quantum information and quantum measurement. Here, we present the broadband bright pulsed squeezed states generated by a single‐pass optical parametric amplification based on a custom‐poled potassium titanyl phosphate crystal. By optimizing the spatial mode of the picosecond pump beams, a bright squeezed light with 1.7 dB squeezing and output power of 5 mW is obtained. With a spatial light modulator, the spatial distribution of the bright squeezed light is shaped into perfect vortex beams with topological charges up to , while the squeezing level is 1.4 dB. The presented squeezed states provide essential resources for advanced quantum optics applications. Graphical Abstract
Light carrying orbital angular momentum (OAM) has many applications ranging from optical manipulation, imaging and remote sensing, and optical communications, and can be used to perform fundamental studies in quantum mechanics and quantum information. Moreover, single photons with high-order OAM allow for increasing the amount of information carried per photon in quantum communication. This thesis describes the study of methods for the preparation and detection of OAM of light in high mode order by utilizing beam shaping techniques using spatial light modulators (SLMs). The quality of the generated high-order OAM mode is limited by optical aberrations which are induced by optical elements in realistic systems and propagation through realistic channels. In order to create and characterize the OAM modes with high quality, we investigate methods for aberration detection and correction using SLMs. These beam shaping techniques for the correction of optical aberrations allow us to generate and detect light carrying OAM with mode order ranging from l = 0 to l = 8 with good quality, and to generate high-quality superpositions of OAM modes with high mode order or in high dimensions. Furthermore, we observe low crosstalk and good levels of mode discrimination between different OAM modes of light. Our experimental setup can be applied in future studies to investigate and test different protocols in quantum information with high dimensional systems, such as high dimensional quantum state tomography.
Squeezed states of light enable enhanced measurement precision by reducing noise below the standard quantum limit. A key application of squeezed light is nonlinear microscopy, where state-of-the-art performance is limited by photodamage and quantum-limited noise. Such microscopes require bright, pulsed light for optimal operation, yet generating and detecting bright pulsed squeezing at high levels remains challenging. In this work, we present an efficient technique to generate high levels of bright picosecond pulsed squeezed light using a χ2 optical parametric amplification process in a waveguide. We measure −3.2dB of bright squeezing with optical power compatible with nonlinear microscopy, as well as −3.6dB of vacuum squeezing. Corrected for losses, these squeezing levels correspond to −15.4−8.7+2.7dB of squeezing generated in the waveguide. The measured level of bright amplitude pulsed squeezing is to our knowledge the highest reported to date, and will contribute to the broader adoption of quantum-enhanced nonlinear microscopy in biological studies.
High-dimensional quantum computing has emerged as a recent alternative to conventional qubit-based approaches, offering advantages such as an increased information density and enhanced robustness against noise. In this work, we explore the use of the orbital angular momentum (OAM) of light as a degree of freedom in which high-dimensional quantum gates can be implemented. We present a theoretical and experimental study of structured light beams carrying OAM, with emphasis on Laguerre–Gauss modes, as a natural basis for high-dimensional quantum computing. We then describe the generation of OAM beams using computer-generated holograms and spatial light modulators, detailing practical methods for encoding arbitrary phase profiles. Building on this framework, we analyze the implementation of high-dimensional quantum logic gates, focusing on the generalized Pauli Z_d and X_d operations. Optical setups based on Dove prisms, Sagnac interferometers, spiral phase plates, and parity sorters are proposed and theoretically validated. Finally, we report experimental results demonstrating the generation of Laguerre–Gauss beams, the transformation properties of Dove prisms, and the operation of a parity sorter, which constitutes a building block for realizing high-dimensional quantum gates. These results establish a solid foundation for future implementations of high-dimensional quantum information processing using the orbital angular momentum of light.