Advancing the frontiers of quantum science and engineering

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.

Abstract: The 176Lu+ ion has a uniqueproperty that it possesses multiple clock transitions. In combination withhyperfine averaging, two of these transitions (1S0 – 3D1and 1S0 – 3D2) present both longlifetimes and low sensitivity to the electromagnetic environment, enabling highperformance clock operation on both transitions. Fully characterizing bothtransitions allows for a frequency ratio measurement within a single ion, whichserves as a well-defined performance metric.This talk focuses on the development of a new ion trapsystem allowing for 3D1 clock comparison at the low 10-19and the calibration of systematics for the 3D2transition. The first part details the design, construction, andcharacterization of the upgraded trap system, which replaces the previous onelimited by high heating rate. The new trap exhibits significantly reducedheating that permits a long Ramsey interrogation time, improved excessmicromotion compensation, and precise characterization of trap rf magneticfield contributing to the ac Zeeman shift. The second part presents anevaluation of 3D2 systematics and the 3D2g-factor measurements with a relative inaccuracy of 10-7. Theg-factor results are used to extract the residual quadrupole moment of the 3D2state arising from hyperfine-mediated effects, corresponding to a frequencyshift at the low 10-19 level.This work demonstrates the suitability of 176Lu+as an optical clock candidate and establishes the experimental capabilitiesnecessary for its continued development toward next-generation opticalfrequency standards.  

Abstract: I will review the properties of probably the simplest system where only two states are available for polariton condensation to occur. This includes a trapped polariton condensate with spin (polarization) degree of freedom or two polariton condensates separated by a barrier. Polariton condensation in this system generally results in the parity symmetry breaking [1], leading also to regular oscillations, or time-crystals [2], and chaos [3]. This system also allows establishing quasi-conservative dynamics with continuous set of closed trajectories in the parity-time symmetric regime, that remain unbroken in the presence of polariton repulsion even at high levels of dissipation imbalance [4]. The quantum theory of polariton dimer [5] demonstrates the coexistence of a symmetry-conserving and symmetry-broken condensates in the vicinity of the threshold, where spontaneous symmetry breaking is reflected in the second-order cross correlator with possibility of the sub-Poissonian polariton statistics.[1] H. Ohadi, A. Dreismann, Y. G. Rubo et al., Phys. Rev. X 5, 031002 (2015). [2] S. Kim, Y. G. Rubo, T. C. H. Liew et al., Phys. Rev. B 101, 085302 (2020). [3] R. Ruiz-Sánchez , R. Rechtman, and Y. G. Rubo, Phys. Rev. B 101, 155305 (2020). [4] I. J. Velázquez-Reséndiz and Y. G. Rubo, Phys. Rev. B 109, 085312 (2024). [5] H. Xu, T. C. H. Liew, and Y. G. Rubo, Phys. Rev. B 110, 075304 (2024).

Abstract: In this tutorial, I will discuss which kinds of codes are possible and which are not by examining the fundamental bounds on quantum error-correcting code parameters (n,k,d). We will begin with the quantum Singleton and Hamming bounds. From there, we will discuss the Gilbert–Varshamov bound, which assures us that high-performance codes theoretically exist, before moving on to the tighter, more realistic constraints imposed by the physical layout of qubits, known as theBravyi–Poulin–Terhal bound. Finally, if time permits, we will touch on how modern computational tools, such as linear and semidefinite programming, are used to numerically search for these precise boundaries.Google calendar invitation for the tutorial series:https://calendar.google.com/calendar/u/0?cid=MTFlY2NmMTQwZjUyZDFkMzE0ZjkzN2RhMmZlYzgyODExMTk5MzljN2M4MTE5YTA2ODVhMTA4Y2EyMzQ3ZTM0MEBncm91cC5jYWxlbmRhci5nb29nbGUuY29tMS Teams link to the tutorial (also in the Google calendar invitation above):https://teams.microsoft.com/l/meetup-join/19%3ameeting_MTcxMjQ1ZDMtZTlkMy00ZWIzLWFjMjgtZDIzNTRiOWJiYmZi%40thread.v2/0?context=%7b%22Tid%22%3a%22a2c8f93f-126b-4596-a360-8941a8984b08%22%2c%22Oid%22%3a%2222c9c804-e027-4233-b645-ddc9fa7b69ad%22%7d 

Abstract: Quantum learning from remotely accessed quantum compute and data must address two key challenges: verifying the correctness of data and ensuring the privacy of the learner's data-collection strategies and resulting conclusions. The covert (verifiable) learning model of Canetti and Karchmer (TCC 2021) provides a framework for endowing classical learning algorithms with such guarantees. In this work, we propose models of covert verifiable learning in quantum learning theory and realize them without computational hardness assumptions for remote data access scenarios motivated by established quantum data advantages. We consider two privacy notions: (i) strategy-covertness, where the eavesdropper does not gain information about the learner's strategy; and (ii) target-covertness, where the eavesdropper does not gain information about the unknown object being learned. We show: Strategy-covert algorithms for making quantum statistical queries via classical shadows; Target-covert algorithms for learning quadratic functions from public quantum examples and private quantum statistical queries, for Pauli shadow tomography and stabilizer state learning from public multi-copy and private single-copy quantum measurements, and for solving Forrelation and Simon's problem from public quantum queries and private classical queries, where the adversary is a unidirectional or i.i.d. ancilla-free eavesdropper. The lattermost results in particular establish that the exponential separation between classical and quantum queries for Forrelation and Simon's problem survives under covertness constraints. Along the way, we design covert verifiable protocols for quantum data acquisition from public quantum queries which may be of independent interest. Overall, our models and corresponding algorithms demonstrate that quantum advantages are privately and verifiably achievable even with untrusted, remote data. https://arxiv.org/abs/2510.07193

Abstract: This introductory talk visits the ultraviolet catastrophe, atomic bombs, atomic clocks, transistors, superconductivity, quantum entanglement and more. Find out how quantum physics has given us modern technologies and what future applications of quantum technologies could look like. There will be time left at the end of the talk for a Q&A session. Come with your burning questions! https://www.nlb.gov.sg/main/whats-on/event-detail?event-id=176102726630

Abstract: Progress toward a three qubit trapped ion quantum computer is reported. Independent control and readout of three 171Yb+ ions are achieved using a multi channel acousto optical modulator together with a multi channel photomultiplier tube. Intensity crosstalk errors are characterized, and compensation pulses are introduced to reduce these errors. The Mølmer–Sørensen two qubit gate is demonstrated across all three ion pairs. Single qubit gate performance is assessed via standard randomised benchmarking. Leading sources of gate infidelities are identified and mitigation strategies described. To end, the set-up is instead used as a quantum sensor, demonstrating that a single trapped ion is sensitive to mechanical vibrations of the vacuum chamber.

Abstract: Recent progress has brought physical error rates close to the threshold required for Quantum Error Correction (QEC). Yet, achieving reliable, high-fidelity operation at scale remains an open challenge. As systems grow, accurately characterizing noise becomes increasingly difficult: scaling up introduces intricate interactions among qubits, where crosstalk, non-Markovian dynamics, and parameter drift create emergent behavior that escapes traditional noise models. The resulting cascade of context-dependent effects exposes the limits of current abstractions and calls for a rethinking of the quantum computing stack and the gate model itself. In this talk, I will introduce a framework that aims to address this issue by extending the traditional gate model of quantum computing. Leveraging state-of-the-art control systems such as NVIDIA’s DGX Quantum, this architecture enables the fine-tuning of the pulse-level description of elementary circuit building blocks based on their particular location within a wider quantum circuit context, without any memory or execution overhead. I will also present a novel and efficient reinforcement learning framework that provides a fast, model-free way to infer and compensate for complex correlated errors, showing how AI-driven calibration can be embedded within the control system to achieve and maintain stability in minutes rather than the hours required by traditional closed-loop approaches. The presentation will conclude with an outlook on architectures enabling concurrent real-time decoding and adaptive in situ calibration during QEC operations. This approach illustrates how the relationship between physical and logical error rates must evolve dynamically to account for drift and circuit dependence, underscoring the importance of hybrid classical–quantum integration in the pursuit of practical fault tolerance.

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.