We exploit quantum information processing on a traveling wave of light, expecting emancipation from thermal noise, easy coupling to fiber communication, and potentially high operation speed. Although optical memories are technically challenging, we have an alternative approach to apply multi-step operations on traveling light, that is, continuous-variable one-way computation. So far our achievement includes generation of a one-million-mode entangled chain in time-domain, mode engineering of nonlinear resource states, and real-time nonlinear feedforward. Although they are implemented with free space optics, we are also investigating photonic integration and performed quantum teleportation with a passive liner waveguide chip as a demonstration of entangling, measurement, and feedforward. We also suggest a loop-based architecture as another model of continuous-variable computing.
We exploit quantum information processing on a traveling wave of light, expecting emancipation from thermal noise, easy coupling to fiber communication, and potentially high operation speed. Although optical memories are technically challenging, we have an alternative approach to apply multi-step operations on traveling light, that is, continuous-variable one-way computation. So far our achievement includes generation of a one-million-mode entangled chain in time-domain, mode engineering of nonlinear resource states, and real-time nonlinear feedforward. Although they are implemented with free space optics, we are also investigating photonic integration and performed quantum teleportation with a passive liner waveguide chip as a demonstration of entangling, measurement, and feedforward. We also suggest a loop-based architecture as another model of continuous-variable computing.
We investigate experiments of continuous-variable quantum information processing based on the teleportation scheme. Quantum teleportation, which is realized by a two-mode squeezed vacuum state and measurement-and-feedforward, is considered as an elementary quantum circuit as well as quantum communication. By modifying ancilla states or measurement-and-feedforwards, we can realize various quantum circuits which suffice for universal quantum computation. In order to realize the teleportation-based computation we improve the level of squeezing, and fidelity of teleportation. With a high-fidelity teleporter we demonstrate some advanced teleportation experiments, i.e., teleportation of a squeezed state and sequential teleportation of a coherent state. Moreover, as an example of the teleportation-based computation, we build a QND interaction gate which is a continuous-variable analog of a CNOT gate. A QND interaction gate is constructed only with ancillary squeezed vacuum states and measurement-and-feedforwards. We also create continuous-variable four mode cluster type entanglement for further application, namely, one-way quantum computation.
Herewithin we present multiplexed integrated photonics as a realisable route to large-scale quantum technologies. Quantum photonics is one many platforms for experimental demonstrations of quantum information science. The technological advantages afforded by the combination of integrated photonic circuits with multiplexing techniques can enable performance enhancements to make photonics a leading infrastructure for implementation of real-world quantum information systems. For this purpose, we create integrated circuits to solve technical challenges in the fields of quantum cryptography, discrete variable and continuous variable quantum computation. These circuits were fabricated in a facility developed at Griffith University, Centre for Quantum Dynamics, for the production of annealed and reverse proton exchange waveguides in congruent lithium niobate and have found applications across the fields of quantum optics and cryptography. We develop and demonstrate the first integrated many-mode active optical demultiplexing of single photons from a solid-state source. This scheme enables the production of a multiphoton Fock state across multiple spatial modes from a single high brightness solid-state source with temporal indistinguishability. This work addressed a major hurdle in the development of photonic quantum computers, namely generation of a large number of indistinguishable single photons on demand. To perform the demultiplexing of single photons we develop two key technologies; a high-speed 1:4 integrated photonic switch and a many channel arbitrary pulse sequence generator. Cryptography as a field is increasingly reliant on quantum random number generators for added security. With increased demand comes a requirement for higher bitrate random number generators, and as such we demonstrate multiplexing of a random number generation scheme based on measurements of quantum vacuum fluctuations. Furthermore, we show an increased level of security at high bitrates by implementing a new signal processing scheme We demonstrate integrated generation, manipulation and homodyning of squeezed light on a single chip for the first time. This scheme is the first successful demonstration of full integration of all the major components needed for continuous variable quantum computation in a temporally multiplexed architecture. These results represent contributions to several fields of study, demonstrating the advantages of integrated quantum photonic multiplexing, and are of interest to the quantum computing, information security, integrated optics, and electronic control communities.
Summary form only given. We are working on hybrid quantum information processing, which combines two methodologies of quantum information processing - qubit and continuous variable (CV) [1]. More precisely, we encode logical qubits by using CV methodology and utilize CV quantum processors for the realization of a fault-tolerant large-scale universal optical quantum computer. The advantage of this methodology is that we can have both high-fidelity nature of qubits and determinisity of CV quantum processors. In other words, we can enjoy both particle- and wave-nature of quantum mechanics. Towards this goal we performed various things, which include quantum error correction with nine-party CV entanglement [2], teleportation of Schrödinger's cat state [3], adaptive homodyne measurement with phase-squeezed states [4], deterministic teleportation of time-bin qubits [5], creation of ultra-large-scale CV cluster states [6], generation and measurement of CV entanglement on a chip [7], and synchronization of photons with cavity-based quantum memories [8].
Enabling large-scale and high-speed quantum computation is a key to practical quantum computation. Continuous-variable approach in optical systems offer advantages in scalability and speed by leveraging their temporal degree of freedom and inherent large carrier frequency. In this paper, we investigate the generation and manipulation of quantum entanglement through a time-domain multiplexing approach. By employing time-domain multiplexing, we generate a two-dimensional cluster state—a universal resource for large-scale quantum computation—and perform quantum operations in the time domain with cluster state. Additionally, our ongoing research focuses on the generation and measurement of broadband optical quantum entanglement through an optical parametric oscillator, which holds potential as a foundation for high-speed quantum computing surpassing limitations of existing systems. By further engineering the quantum entanglement, we have also theoretically formulated a practical teleportation-based architectures for quantum computation in time domain. These advancements form the groundwork for the development of practical optical quantum computation.
Photonics quantum networks play a crucial role in quantum information processing by enabling efficient distribution and manipulation of quantum states of light. Femtosecond pulses, when combined with nonlinear interactions, generate entangled multimode outputs, which can be enhanced through mode-selective homodyne detection, forming quantum cluster states. These naturally arising nonlinearities and correlations, integrated with optical or electronic feedback, serve as a foundation for quantum reservoir computing (QRC). We present a scalable, room-temperature approach to quantum computing without single-photon sources or detectors. We report a proof-of-principle experimental realization of QRC using pump phase encoding with electronic feedback, with ongoing efforts focused on optimizing implementations through pulse shaping. Additionally, we explore a novel measurement-based QRC protocol using cluster states and teleportation, where measurements drive input encoding, processing, and time series monitoring.
Quantum squeezed states of light can enhance measurement sensitivity beyond classical limits and enable quantum information processing, but scalable low-loss sources remain challenging. We demonstrate continuous-wave quantum squeezing on a chip, achieving 18 dB of squeezing and 20 dB of anti-squeezing at 1570 nm in a 1.6-cm traveling-wave adaptively poled thin-film lithium niobate waveguide. A distributed model independently determines facet losses, phase noise, and nonlinear interaction strength without prior assumptions, enabling rigorous inference of on-chip performance. We estimate a 95% confidence interval of [-18.96, -17.25] dB squeezing and [19.96, 21.35] dB anti-squeezing. These values represent the highest squeezing reported for any integrated photonic platform and the first assumption-free statistical validation of integrated squeezing performance. Our results establish thin-film lithium niobate as a high-performance, scalable platform for continuous-variable quantum sensing, communications, and photonic computing.