The concept of quantum steering was originally introduced by Schrödinger to describe the "spooky action-at-a-distance" effect noted in the Einstein-Podolsky-Rosen (EPR) paradox, whereby local measurements performed on one party apparently adjust (steer) the state of another distant party. In this talk, I will give an introduction about the advances of the EPR steering and its advantage as quantum resource. Then I will present our efforts on characterizing bipartite and multipartite steering and developing its unique applications in quantum information processing. I will give an overview of our recent developments on quantum steering and its applications in quantum information. I will share our view about the current challenges, opportunities and the future directions for this topic.

Sculpted light refers to the generation of custom designed light fields. These light fileds can be applied in many diverse fields ranging from interrogating single atoms or atom assembly to using these fields for optical micromanipulation and optical tweezers as well as creating new quantum devices and sensors. We consider here the study and application of light with structured intensity, polarization and phase. We can create custom fields in multiple planes using dynamic and geometric phase control. As an example, the use of sculpted light in imaging has led to superresolution microscopy developed by Betzig, Hell and Moerner (2014 Nobel prize in Chemistry). Sculpted light can be generated using several technologies. These are spatial light modulators (SLM) and Digital Micromirror Devices (DMD) that enable the production of configurable and flexible confining potentials at the nano and micron-scale. Sculpted light can also be produced using time averaged methods such as Acousto-Optics Modulators (AOM), enabling production of highly configurable time-averaged traps. All these methods achieve dynamical and flexible sculpted light fields and enable imaging of the amplitude patterns, phase and polarization. Using these sculpted light we can produce novel optical potentials which can be used for intricate studies of light -matter interactions in a variety of environments. We will describe their use ranging from studies such as quantum thermodynamics using ultra cold atoms to trapping and manipulating nano and micron-size objects or even making measurements in-vivo inside biological cells.

This conference presentation was prepared for the Quantum and Nonlinear Optics IX conference at SPIE/COS Photonics Asia 2022.

Controlling and programming quantum devices to process quantum information by the unit of qudit shows great potential to enhance the capabilities of qubit-based quantum technologies. Here, we report a programmable qudit-based quantum processor in silicon-photonic integrated circuits and demonstrate its enhancement of quantum computational parallelism. The processor monolithically integrates all the key functionalities and capabilities of initialisation, manipulation, and measurement of the two-ququart states and multi-value quantum-controlled logic gates with high-level fidelities. We implemented the basic quantum Fourier transform algorithms to benchmark the enhancement of quantum parallelism using qudits, allowing the implementations of more than one million high-fidelity preparations, operations and projections of qudit states in the processor. Our work shows an integrated quantum technology for qudit-based quantum computing with enhanced capacity, accuracy, and efficiency.

High performance quantum memory for quantized states of light is a building block of quantum information technology. Despite great progresses of optical quantum memories based on interactions of light and atoms, physical features of these memories still cannot satisfy requirements for applications in practical quantum information systems, since all of them suffer from trade off between memory efficiency and excess noise. Here, we report a high-performance cavity enhanced electromagnetically induced transparency memory with warm atomic cell in which a scheme of optimizing the spatial and temporal modes based on the time-reversal approach is applied. The memory efficiency up to 67 ± 1% is directly measured and atom interaction, and a noise level close to quantum noise limit is simultaneously reached, which enable the high fidelity quantum memory. Thus, the realized quantum memory platform is ready to be applied in quantum information systems.

This conference presentation was prepared for the Quantum and Nonlinear Optics IX conference at SPIE/COS Photonics Asia 2022.

Due to the inevitable loss of single photon transmission in optical fiber, a quantum repeater scheme is needed to establish large-scale quantum networks. The existing elementary quantum repeater links are all based on emissive quantum memories, with entangled photons emitted by the memory itself. This architecture is difficult to support deterministic photon emission and multiplexing storage simultaneously, which fundamentally limits the rate of entanglement distribution. In this talk, I will present our recent work about the realization of heralded quantum entanglement between two absorptive quantum memories based on rare-earth-ion-doped crystals. This work confirmed the feasibility of constructing quantum repeater based on absorptive quantum memories and demonstrated the acceleration effect of multiplexing in quantum repeater for the first time, which lays a solid foundation for the construction of practical high-speed quantum networks.

Quantum random number generators can provide genuine randomness by exploiting the intrinsic probabilistic nature of quantum mechanics, which play important roles in many applications. However, the true randomness acquisition could be subject to attacks from untrusted devices involved or their deviations from the theoretical modelling. Here we propose and experimentally demonstrate a source-device-independent quantum random number generator, which enables one to access true random bits with an untrusted source device. The random bits are generated by measuring the arrival time of either photon of the time-energy entangled photon pairs produced from spontaneous parametric down conversion, where the entanglement is testified through the observation of nonlocal dispersion cancellation. In experiment we extract a generation rate of 1.125 Mbps by modified entropic uncertainty relation. Our approach provides a promising candidate for quantum random number generators with no characterization.

Optical microcavities are inherently non-Hermitian in nature, offering a fertile ground to test recent emerging development in non-Hermitian physics. Among them, representative examples include coherent perfect absorption (CPA)/critical coupling, electromagnetically induced transparency (EIT), parity-time symmetric coupled resonators, exceptional points (EP). In this talk, we shall discuss our group’s efforts in non-Hermitian optics in a single microcavity by extending an additional dimension such as frequency through internal nonlinear optical processes. Within a single whispering-gallery-mode type microcavity, we show nonlinearity can alter the total transmission of a CPA, examining such a critical coupling mechanism in the nonlinear regime. Similarly, we demonstrate a new mechanism of optically induced transparency in a micro-cavity by introducing a four-wave mixing gain to nonlinearly couple two separated resonances of the micro-cavity in an ambient environment.

In this talk, I will discuss the recent advances in exploring novel photonics with the construction of synthetic frequency dimension through the electro-optic modulation, where light can be manipulated in linear and nonlinear ways. In particular, I will discuss the way to construct a one-dimensional Lieb lattice and explore the transition between flat and non-flat bands in the synthetic space. Our work shows a significant step towards constructions of more complicated lattices in multiple rings. Moreover, I will propose a unique method to explore the topological non-equilibrium dynamics and capture the topological invariant with information only in the time dimension, by building an effective spin model in multiple rings associated with synthetic frequency dimensions. Finally, I will talk about the opportunity for studying nonlinear effects in the synthetic space, once the four-wave mixing process is considered.

With the widespread use of complex electrical parts composed of nanomaterials in optoelectronic and energy field, the evolution of electrical properties for these components in real operation condition should be mastered. In this work, we demonstrate a quantum-based magnetic imaging apparatus that can directly monitor the nanoscale current dynamics of complex networks noninvasively. We investigate the change of current distribution of silver nanowire networks during direct current (DC) and alternating current (AC) electrical annealing. We observe some reported phenomena at nanoscale, such as winner-takes-all dominated network under low DC voltage stress and “life” in crack during breakdown. Besides, by AC electrical annealing the stability difference of networks with high and low density are directly distinguished. Our technique is well suited for various complex network to image the dynamics of nanoscale current paths.