Advancing the frontiers of quantum science and engineering

Abstract: Satellite-based quantum communication offers a promising pathway to establishing a global quantum network, enabling long-distance quantum key distribution (QKD) and entanglement distribution beyond the reach of terrestrial fibre links. This work presents the development of Singapore's satellite-based quantum communication infrastructure, centered on the Singapore Optical Ground Station (SOGS), the first optical ground station commissioned near the equator, located at the National University of Singapore. The core contribution is the development and deployment of the Optical Receiver Unit (ORU), which couples the incoming satellite beam into multi-mode fibre outputs for downstream quantum signal detection. The ORU integrates three subsystems: a Pointing, Acquisition, and Tracking (PAT) system achieving arcsecond-level closed-loop tracking accuracy; a polarisation correction system using motorised half-wave plates; and quantum receiver analysing photons across four standard polarisation channels. SOGS operations are discussed, with first light successfully received from the SpeQtre 12U CubeSat, an entangled photon satellite launched in November 2025 by SpeQtral and RAL Space UK. The ORU reconfigurable architecture is demonstrated at both SOGS and the ESA Optical Ground Station in Tenerife, Spain, confirming adaptability to different telescope focal configurations. Successful QKD demonstrations with SpeQtre across the Singapore and Tenerife ground stations will constitute a critical milestone in this work, towards the realisation of a global scale trusted-node quantum network.

Abstract: Bell non-locality is a powerful framework to distinguish classical, quantum and post-quantum resources, which relies on non-communicating players. Under which restriction can we have the same separations, if we allow for communication? Non-signalling state assemblages, and the fact that they can always be simultaneously purified, turned out to be the key element to restrict the simplest bipartite communication scenario, the prepare-and-measure, to the standard bipartite Bell scenario. Yet, many distinctive features of quantum theory are genuinely multipartite and cannot be reduced to two-party behaviour. In this work we are interested in extending this simultaneous purification inspired result to all multipartite communication schemes. As a first step, we unify and extend the simultaneous purification result from states to instruments and super-instruments, which are composable structures, and open up the possibility to explore more complex communication scenarios. Our main contribution is to establish that arbitrary compositions of non-signalling assemblages cannot escape the standard spatial quantum Bell correlations set. As a consequence, any interactive quantum realization of correlations outside of this set must involve at least one signalling assemblage of quantum operations, even when the resulting correlations are non-signalling. This talk is mostly based on the following work: https://arxiv.org/abs/2601.05158. If time allows, we will also hint at the connection to compiled non-local games and the operator-algebraic generalisation of these results, presented in https://arxiv.org/abs/2507.12408

TBA

Abstract: Quantum memory and entanglement generation are key components of scalable quantum networks. Among various platforms, spin ensembles offer a promising approach due to their strong collective coupling to cavity fields and intrinsic multimode storage capacity. However, accurate numerical simulation of spin-ensemble systems, particularly for quantum noise and correlation functions, remains challenging, largely due to the coexistence of inhomogeneous broadening in both spin frequencies and spin–cavity coupling strengths. In this work, we develop a GPU-accelerated numerical framework based on second-order cumulant expansion to capture mean values and correlations, together with the quantum regression theorem to evaluate two-time correlation functions and quantum noise. We apply this approach to both the Revival of Silenced Echo (ROSE) quantum memory protocol and the Rephased Amplified Spontaneous Emission (RASE) entanglement generation protocol. Our results reproduce key predictions of recently developed theoretical work from our group and demonstrate that in the ROSE protocol with adiabatic rapid passage (ARP) pulses, noise in the retrieved signal is suppressed by inhomogeneous broadening of the spin–cavity coupling. In the RASE protocol, we further show that appropriately designed composite ARP pulses preserve the generated entanglement. These results provide practical guidance for the design of quantum memory and entanglement generation protocols.

Abstract: The 176Lu+ 1S0 → 3D1 transition serves as a robust frequency reference due to its low sensitivity to blackbody radiation and electromagnetic perturbations, allowing for high-accuracy operation at room temperature without extensive shielding [1]. Building on recent advances in micromotion control [2], quadrupole shift assessment [3], and studies of background gas collision effects [4], we report a comprehensive evaluation of two independent 176Lu+ single-ion optical frequency references, achieving total systematic uncertainties of 1.1 × 10−19 and 1.4 × 10−19 [5]. The two systems were directly compared using correlation spectroscopy with Ramsey times of up to 10 seconds, yielding a measurement instability of 4.8 × 10−16(τ/s)−1/2. After 200 hours of averaging, the clocks demonstrated a relative frequency agreement of [−2.4 ± (5.7)stat ± (1.0)sys] × 10−19 [5]. While other individual clocks have reported assessed uncertainties below 10−18, this work represents the first demonstrated agreement of optical clock performance with total uncertainty below this level. These results open the way for new applications in millimeter-scale relativistic geodesy and tests of fundamental physics at the 10−19 frontier of accuracy.

Abstract: Organised by Singapore’s Centre for Quantum Technologies (CQT), the hackamonth is an innovative approach to hackathons: a month-long, collaborative experience where participants work on quantum computing for meaningful problems. Typical hackathons are short and competitive, ending with prizes. With our hackamonth, we want to have real scientific impact.

Abstract: QCamp is a one-week summer school for curious and inquisitive minds who wish to explore and understand the physical laws that govern the world’s smallest scales: quantum physics. The scope of QCamp is to provide vivid demonstrations of these laws, offer career advice, as well as to help students build a technical foundation for independent exploration of this world. QCamp is organised by the Centre for Quantum Technologies (CQT) at the National University of Singapore.

The one-day Flash QCamp for curious and inquisitive minds to get a taster in quantum technologies.

The Quantum Information Processing Conference (QIP) is the largest quantum information processing technology conference, which annually gathers the world’s brightest researchers and industry leaders for a week long program to present and discuss the latest achievements in quantum computing, cryptography, information theory, mathematics and physics. Recent editions have drawn nearly 1000 participants. In 2027, CQT will host the 30th edition of this conference in Singapore. QIP2027 will take place 20-26 February 2027.

The International Conference on Women in Physics (ICWIP) of the International Union of Pure and Applied Physics (IUPAP) will take place in the National University Singapore (NUS) during 7-11 June 2027, hosted by the Physics Department, NUS and the Centre for Quantum Technologies, Singapore. The ICWIP2027 is the 9th in a series of triennial conferences by IUPAP since 2002 that brings together practitioners from all over the world in order to deliberate on both topics in physics and processes within physics practice, with the goal of transforming physics into a welcoming inclusive enterprise for everyone. The conference will feature inspiring keynote talks by eminent women scholars, sessions where participants can present their own research in physics and on equity and inclusion in physics, interactive workshops to engage with the barriers to equity and inclusion in physics, call-to-action sessions on recommendations for the profession and more...