09:00  10:00

Hannes Bernien
(University of Chicago)
A dualspecies Rydberg array
Rydberg atom arrays have emerged as a leading platform for quantum information science. Reaching system sizes of hundreds of longlived qubits, these arrays are used for highly coherent analog quantum simulation, as well as digital quantum computation. Advanced quantum protocols such as quantum error correction, however, require midcircuit qubit operations, including the replenishment, reset, and readout of a subset of qubits. A compelling strategy to achieve these capabilities is a dualspecies architecture in which a second atomic species can be controlled without crosstalk, and entangled with the first via Rydberg interactions.
In this talk, I will introduce our dualspecies Rydberg array consisting of rubidium (Rb) and cesium (Cs) atoms and present new regimes of interactions and dynamics not accessible in singlespecies architectures. I will share our recent results on interspecies interactions which we use to realize Rydberg blockade and implement quantum state transfer from one species to another. Furthermore, we generate a Bell state between Rb and Cs hyperfine qubits via an interspecies controlledphase gate. Finally, we combine interspecies entanglement with native midcircuit readout to achieve quantum nondemolition measurement of a Rb qubit using an auxiliary Cs qubit. These techniques are crucial ingredients for scalable measurementbased protocols and realtime feedback control in largescale quantum systems.

10:00  11:00

Henrik Dreyer
(Quantinuum)
LongRange Entangled States in Trapped Ions from Measurement and FeedForward
Quantum devices have matured to the point where multipartite entanglement can be created on 30+ qubits. One important capability of these devices is the creation of longrange entangled states, both as initial states for quantum simulation and for error correction within the same devices. Unfortunately, by definition, topologically ordered states require extensive unitary circuit depths for their preparation, which places constraints on the coherence times of nearterm devices. I will talk about how constantdepth protocols based on measurement and feedforward have recently been used to prepare toric code and nonAbelian topological order on Quantinuum's Hseries trappedion computers.

11:00  11:30

group photo (to be published on the event website) & coffee break

11:30  12:30

Ruben Verresen
(Harvard University)
Which states of matter can be prepared using measurement?

12:30  13:30

lunch

13:30  14:00

discussion

14:00  15:00

Tibor Rakovszky
(Stanford University)
Defining phases of active quantum matter
The latest generations of quantum devices are rapidly developing the technology needed to perform realtime ("midcircuit") measurements and feedback, giving us access to highly controlled far from equilibrium "active" quantum systems. This provides a large new arena for quantum manybody physics, and in my talk I will discuss the problem of defining robust quantum phases of matter in such nonequilibrium open systems. I will formulate conditions for the stability of these phases, putting it on a similar footing to the wellestablished theory of zero temperature phases of gapped quantum matter. Our formulation leads to desirable features, such as the robustness of longrange correlations within the phase, and I will describe physical mechanisms that give rise to such stability. These fundamental questions in manybody physics are also closely related to the problem of quantum error correction, particularly the problem of finding selfcorrecting codes that do not require nonlocal classical communication between the quantum device and a classical processor.
TR, Sarang Gopalakrishnan, Curt von Keyserlingk: Defining stable phases of open quantum systems, ArXiv 2308.15495

15:00  15:30

coffee break

15:30  16:30

Sagar Vijay
(University of California)
The Stability of Gapped Quantum Matter and ErrorCorrection with Adiabatic Noise
The codespace of a quantum errorcorrecting code (QECC) can often be identified with the groundspace within a gapped phase of quantum matter. We argue that the stability of such a phase is directly related to a set of coherent error processes against which this quantum errorcorrecting code is robust: such a quantum code can recover from adiabatic quantum channels, corresponding to random adiabatic drift of code states through the phase, and with asymptotically perfect fidelity in the thermodynamic limit, as long as this adiabatic evolution keeps states sufficiently close to the initial groundspace. We further argue that when specific decoders  such as minimumweight perfect matching  are applied to recover this information, an errorcorrecting threshold is generically encountered within the gapped phase. In cases where the adiabatic evolution is known, we explicitly show examples in which quantum information can be recovered by using stabilizer measurements and Pauli feedback, even up to a phase boundary. This provides examples in which nonlocal, coherent noise effectively decoheres in the presence of syndrome measurements in a stabilizer QECC.

16:30  17:30

Andreas Elben
(Caltech)
Characterizing Noisy IntermediateScale Quantum Dynamics: Conservation Laws and Target State Fidelities (remotely talk)
In my talk, I will present protocols and experimental results for characterizing noisy intermediatescale quantum dynamics. Firstly, I will introduce a learning algorithm designed to discover conservation laws given as sums of geometrically local observables in unknown dynamics. This algorithm leverages the classical shadow formalism for estimating expectation values of observables to identify all such conservation laws with rigorous performance guarantees. I will present numerical experiments that illustrate the algorithm's application in the context of lattice gauge theories and manybody localization.
Secondly, I will introduce benchmarking protocols for quantum devices that rely on estimating fidelity to target states. I will particularly focus on highlyentangled quantum states generated by ergodic quantum dynamics, where emergent randomness enables efficient fidelity estimation schemes. Experimental results from a 60atom Rydberg quantum simulator at the threshold of exact classical simulatability will be presented. Utilizing the extracted fidelity, I will also demonstrate a novel estimator for experimental mixedstate entanglement, showing that the Rydberg quantum simulator is competitive with stateoftheart digital quantum devices performing random circuit evolution.

17:30  18:00

discussion

18:00  19:00

dinner
