Talks

In this talk, I will discuss quantum diagonalization methods, based on subspaces obtained from quantum computers, which overcome the scaling limitations of variational algorithms and enabled realistic chemistry computations of up to 77 qubits on a quantum centric supercomputing architecture, using a Heron quantum processor and the RIKEN supercomputer Fugaku. Merging these ideas with Krylov quantum subspaces, I will present a ground state algorithm with convergence similar to phase estimation and robustness to noise, which led to an experimental demonstration for lattice ground state problems obtained with Heron processors and the supercomputer Frontier.

Gravitational wave observations have unveiled the population of merging black holes and neutron stars, providing direct access to strong-field gravity and dense nuclear matter. These compact binaries emit gravitational radiation as they inspiral and merge, producing waveforms that encode: the masses and spins of the constituents, neutron star's equation of state, the properties of gravity in extreme regimes, and details of their astrophysical environments. Extracting this information requires precise theoretical predictions for comparison with observations. Next-generation detectors, both ground and space-based, are expected to observe 10^3-10^5+ cycles of a given binary merger, with potentially many thousands of events per year across disparate regimes of masses, eccentricities, etc. At this scale, numerical relativity simulations alone become computationally prohibitive, making precision analytical calculations essential.

In this talk I will present new analytical approaches to the gravitational two-body problem that combine effective field theory techniques from particle physics together with tools from General Relativity. I will discuss methods for computing the dynamics of isolated binaries at high perturbative orders, as well as methods for describing binaries embedded in gaseous or dark matter environments where environmental effects modify the orbital evolution and gravitational wave signal.

In order to achieve fault-tolerant quantum computing, we make use of quantum error correction schemes designed to protect the logical information of the system from decoherence. A promising way to preserve such information is using the multimode Gottesman-Kitaev-Preskill (GKP) encoding, which encodes a single logical qubit into harmonic oscillators. This type of encoding adds redundancy in the physical system by leveraging the infinitely large Hilbert space of multiple oscillators. Such redundancy can be used to increase the distance between the logical code words, protecting the logical qubit against larger errors. Usual protocols to correct multimode GKP states are based on Steane-type quantum error correction circuits. Steane-type circuits consist of auxiliary state preparation, two-mode squeezing operations, measurements and decoding. In this work, we focus on the decoding part of these protocols. More precisely, we propose a decoder that considers the noise present on the auxiliary states. Specifically, we do so by tracking the correlations between errors on different modes spreading throughout the circuit which represents the Steane-type protocol. We show that leveraging the correlations between the measurement result and the actual error affecting the multimode GKP state enables less decoding errors. Overall, for each different multimode GKP code studied, we can increase the lifetime by at least an order of magnitude, yielding more robust quantum computation.

Quantum error correction (QEC) is believed to be essential for the realization of large-scale quantum computers. However, due to the complexity of operating on the encoded `logical' qubits, understanding the physical principles for building fault-tolerant quantum devices and combining them into efficient architectures is an outstanding scientific challenge. Here we utilize reconfigurable arrays of up to 448 neutral atoms to implement all key elements of a universal, fault-tolerant quantum processing architecture and experimentally explore their underlying working mechanisms. We first employ surface codes to study how repeated QEC suppresses errors, demonstrating 2.14(13)x below-threshold performance in a four-round characterization circuit by leveraging atom loss detection and machine learning decoding. We then investigate logical entanglement using transversal gates and lattice surgery, and extend it to universal logic through transversal teleportation with 3D [[15,1,3]] codes, enabling arbitrary-angle synthesis with logarithmic overhead. Finally, we develop mid-circuit qubit re-use, increasing experimental cycle rates by two orders of magnitude and enabling deep-circuit protocols with dozens of logical qubits and hundreds of logical teleportations with [[7,1,3]] and high-rate [[16,6,4]] codes while maintaining constant internal entropy. Our experiments reveal key principles for efficient architecture design, involving the interplay between quantum logic and entropy removal, judiciously using physical entanglement in logic gates and magic state generation, and leveraging teleportations for universality and physical qubit reset. These results establish foundations for scalable, universal error-corrected processing and its practical implementation with neutral atom systems.

We present a family of simple three-dimensional stabilizer codes, called the chiral color codes, that realize fermionic and chiral topological orders. In the qubit case, the code realizes the topological phase of a single copy of the fermionic toric code. For qudit systems with local dimension d, the model features a chiral parameter α and realizes 3D topological phases characterized by $\mathbb{Z}^\alpha_d$ anyon theories with anomalous chiral surface topological order. On closed manifolds, the code has a unique ground state after removing bulk transparent fermions or bosons. Furthermore, we prove that the bulk is short-range entangled (for odd d, coprime α) by constructing an explicit local quantum channel that prepares the ground state. The chiral color codes are constructed within the gauge color code, and hence inherit its fault-tolerant features: they admit single-shot error-correction and allow code switching to other stabilizer color codes. These properties position the chiral color codes as particularly useful platforms for realizing and manipulating fermions and chiral anyons.