Advancing the frontiers of quantum science and engineering

Abstract: In this talk, I will present our recent work on testing conditional independence in discrete probability distributions, as well as an outline of the corresponding problem for testing quantum states, along with existing approaches.   Given samples from a joint distribution over multiple variables, we test whether two variables are conditionally independent given a third, or whether they have minimal conditional mutual information. Our approach reduces the problem to a refined form of equivalence testing, and we also show optimality of the sample complexity in several parameter regimes.   As a natural extension, we are interested in the sample complexity of testing multipartite quantum states for (conditional) independence, where we hope to benefit from parallels to the classical case. I will present relevant existing results and open problems in the quantum setting.

Abstract: A critical component in the realisation of a global quantum network is the coupling between photons at the optical and microwave frequencies. A well-known promising candidate to build the key quantum light-matter device are rare earth ions (REIs). However, to achieve efficient optical interface with the REIs, a tuneable high quality factor resonator is required to leverage Purcell enhancement. Here, we focus on the application of thin film lithium niobate (LN) photonic integrated chips, incorporating microring resonators, to interface with an erbium-doped calcium tungstate (CaWO4) host crystal.

Abstract: Manipulating quantum phenomena of microscopic particles to emulate novel states of matter and establish high-precision time standards promises to greatly advance future technological developments. Techniques involving ultracold atoms have formed a nexus between disciplines such as quantum information science, condensed matter physics, and quantum precision measurement, positioning them at the forefront of hot research areas in physics. In this talk, I will introduce the latest developments in quantum manipulation based on ultracold fermionic systems for quantum simulation and quantum metrology in USTC. In quantum simulation, systems comprising hundreds up to millions of atoms can be artificially created and controlled to mimic complex systems found in condensed matter physics and quantum field theory. This facilitates the validation or prediction of novel quantum phenomena, exploration of the underlying microscopic mechanisms, and fosters the next generation of technological and industrial revolutions. Utilizing small-scale and manageable ultracold fermionic systems, important unsolved models in condensed matter physics like the Fermi-Hubbard model can be simulated, aiming to acquire phase diagrams of strongly correlated fermionic systems at low temperatures. In the field of quantum metrology, ultracold atomic optical lattice clocks have achieved the highest time measurement accuracy to date. To overcome limitations such as gravitational fluctuations in terrestrial and near-Earth environments, there is an urgent need to develop optical frequency standards based on high-orbit space platforms. Ultracold atomic optical lattice clocks on medium-to-high orbit space platforms, integrated with quantum communication and time-frequency transfer technologies, will enable precise star-to-ground clock comparisons and become a key component in the next generation of optical clock-based second definitions.

Quantum Techniques in Machine Learning (QTML) is a leading international conference at the forefront of quantum science and machine learning. Held annually, it brings together researchers and industry experts to explore how quantum computing can transform learning, optimisation, and data-driven discovery. CQT is proud to support planning for the ninth edition of this international conference, QTML 2025, to take place in Singapore 16-21 November. Registration is now open.

The goal of this workshop is to bring the active research community together to discuss the progress, challenges and new possible directions for quantum repeaters and networks. We invite researchers working on key enabling technologies and system integration, protocols for connecting repeaters across network links with high fidelity, architectures for large-scale networks, and applications of distributed quantum entanglement. The WQRN has been and continues to be a limited-attendance, few-day workshop, in which participants are given the opportunity to share ideas, directions, and concerns to advance the state of the field. Talks are by invitation only and catered to broadly cover the applications, theory, components, and worldwide directions in quantum repeaters and networks. These talks frame group discussion sessions for which all participants are welcome to contribute; participants are also welcome to contribute to a poster session.