Events

Abstract: Non-local quantum computation (NLQC) replaces a localinteraction between two systems with a single round of communication and sharedentanglement. It arises naturally in the analysis of attacks on quantumposition verification (QPV). Despite many partial results, it is known that acharacterization of entanglement cost in at least certain NLQC tasks wouldimply significant breakthroughs in complexity theory. Here, we avoid theseobstructions and take an indirect approach to understanding resource requirementsin NLQC, which mimics the approach used by complexity theorists: we study therelative hardness of different NLQC tasks by identifying resource efficientreductions between them. Most significantly, we prove that f-measure (the taskof measuring in a certain BB84 basis according to a classical function f) andf-route (the task of routing a qubit according to a classical function f), thetwo best studied NLQC tasks, are in fact equivalent under O(1) overheadreductions. This result simplifies many existing proofs in the literature asresults were often proved separately for the two, it also extends several newproperties to f-measure that were only known for f-routing. For instance, weobtain sub-exponential upper bounds on f-measure for all functions.This talk is based on joint work with the same title withAndreas Bluhm, Simon Höfer, Alex May, Mikka Stasiuk and Henry Yuen https://arxiv.org/abs/2505.23893

Abstract: Ultracold polar molecules with their strong long-range and anisotropic dipolar interaction are a promising platform for quantum simulation of many-body physics, quantum information processing and ultracold chemistry. In this thesis, the control of the internal degrees-of-freedom of 6Li-40K molecules is experimentally studied. First, efficient transfer of weakly-bound 6Li-40K Feshbach molecules to their absolute ground state is experimentally achieved with the use of coherent and low-phase noise Raman lasers. In this context, an FPGA-based digital servo is characterized for the stabilization of the low-phase-noise Raman lasers. We compare our digital servo to a commercial analog servo and show that it performs equally in terms of phase noise and linewidth of the stabilized lasers. Control of the rotational and hyperfine states of the 6Li40K ground state molecules is demonstrated by using microwave fields. Rabi oscillations of hundreds of microseconds demonstrate coherent control of these states. Additionally, direct absorption imaging of ground state molecules is achieved with a peak signal-to-noise ratio of 3. This scheme could be useful when indirect imaging (by detecting Feshbach molecules) is not possible. In addition, direct phase contrast imaging of molecules is proposed as an alternative approach.

Abstract: Implementing a quantum circuit on specific hardware with a reduced available gate set is often associated with a substantial increase in the length of the equivalent circuit. This process is also known as transpilation and due to decoherence, it is mandatory to keep quantum circuits as short as possible, without affecting functionality. In this work we propose three different transpilation approaches, based on a localized term-replacement scheme, to substantially reduce circuit lengths while preserving the unitary operation implemented by the circuit. The first variant is based on a stochastic search scheme, and the other variants are driven by a database retrieval scheme and a machine learning based decision support. We show that our proposed methods generate short quantum circuits for restricted gate sets, superior to the typical results obtained by using various qiskit and BQSKit optimization levels. Our method can be applied to different gate sets and scales well with an arbitrary number of qubits.

Abstract: Coherent states conveniently represent the classically meaningful wavelike states of light, as opposed to the corpuscular number states, but superposingcoherent states is mind-bogglingly unclassical, including as examples "cat states", "comb states" and "compass states". I present a history of superposing coherent states, especially for oscillators (including electromagnetic field states) and for spin, and extend to entangled coherent states. I then show that superposed coherent states are a viable path for photonic quantum computing and for reaching towards the ultimate limits of sensing. Finally, I discuss our experimental realisations (at University of New South Wales) of superposed coherent states in a spin-7/2 Antimony nucleus in a silicon substrate.

Abstract: This talk traces the development of quantum physics throughout the 20th century, emphasizing its intricate entanglement with economic, political, and cultural contexts. Unexpected associations—linking streetlights to Planck’s quantum of action, lasers to ballet dancers, and timekeeping to ion traps—serve as narrative threads illustrating the multifaceted nature of quantum discoveries. These examples, drawn from the “Light and Matter” exhibition at the Deutsches Museum in Munich, Germany, offer historical vantage points from which to reflect on the evolving landscape of quantum technologies today.

The workshop concerns both the theoretical and experimental aspects of this subject. This workshop aims to build connections between young scientists and promotes open discussions between participants. As such, 30-minute talks by all participants will be held at the beginning of the week, leaving two full days open for discussions on the presented work (and beyond).

Please note that participation in this workshop is by invitation only.

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.