SQuInT 2021 Program
Full Program | Thursday | Friday | All Sessions | Posters | Talks
SESSION 1: Talks at Zoom | |
| 10:00am-10:30am | Paola Cappellaro, Massachusetts Institute of Technology Quantum simulation with coherent engineering of synthetic dimensions | Abstract The high controllability of engineered qubit systems can be leveraged to explore exotic condensed matter systems by simulating synthetic topological phases of matters. Observation of novel effects can be achieved even in small quantum systems by exploiting their periodic driving, which can mimic the properties of spatially periodic materials and elucidate their symmetry and topological features. Two challenges have so-far prevented such exploration, the lack of an experimentally accessible characterization protocol and of strong-enough driving fields. Here I'll show how to overcome both challenges to achieve the first experimental study of dynamical symmetries and the observation of symmetry-protected selection rules -- and their breaking. I will further show how these methods can be used to synthesize and characterize a tensor monopole in the 4D parameter space described by the spin degrees of freedom of a single solid-state defect in diamond. These results demonstrate the power of coherent control and Floquet engineering for quantum simulation. |
| 10:30am-10:50am | Aleksander Kubica, Amazon Web Services Center for Quantum Computing Single-shot error correction and universal fault-tolerant computation with the 3D subsystem toric code | Abstract We introduce a new topological quantum code, the three-dimensional subsystem toric code (3D STC), which is a generalization of the stabilizer toric code. The 3D STC can be realized by measuring geometrically-local parity checks of weight at most three on the cubic lattice with open boundary conditions. We prove that single-shot quantum error correction (QEC) is possible with the 3D STC, i.e., one round of local parity-check measurements suffices to perform reliable QEC even in the presence of measurement errors. We also explain how to fault-tolerantly implement a universal gate set in the 3D STC without state distillation. Lastly, we propose an efficient single-shot QEC strategy for the 3D STC and investigate its performance. In particular, we numerically estimate the resulting storage threshold against independent bit-flip, phase-flip and measurement errors to be above 1%. Such a high threshold together with local parity-check measurements of small weight make the 3D STC particularly appealing for realizing fault-tolerant quantum computing. |
| 10:50am-11:10am | Bharath Hebbe Madhusudhana, Max-Planck-Institute for Quantum Optics Benchmarking an efficient approximate method for localized 1D Fermi-Hubbard systems on a quantum simulator | Abstract Identifying and understanding the applications of NISQ-era quantum simulators and quantum computers is a topical problem. Quantum many-body physics embodies a unique set of problems that are both computationally hard and physically pertinent and are therefore apt for applications of NISQ devices. While state-of-the art neutral atom quantum simulators have made remarkable progress in studying many-body dynamics, they are noisy and limited in the variability of initial state and the observables that can be measured. Here we show that despite these limitations, quantum simulators can be used to develop new numerical techniques to solve for the dynamics of many-body systems in regimes that are practically inaccessible to established numerical techniques [1]. Considering localized 1D Fermi-Hubbard systems, we use an approximation ansatz to develop a new numerical method that facilitates efficient classical simulations in such regimes. Since this new method does not have an error estimate and is not valid in general, we use a neutral-atom quantum simulator with L_exp = 290 lattice sites to benchmark its performance in terms of accuracy and convergence for evolution times up to 700 tunnelling times. We then use this method to make a prediction of the behaviour of interacting dynamics for spin-imbalanced Fermi-Hubbard systems, which we show to be in quantitative agreement with experimental results. [1.] Bharath Hebbe Madhusudhana et. al. arXiv:2105.06372 |
| 11:10am-11:30am | Christopher Pattison, California Institute of Technology Improved quantum error correction using soft information | Abstract The typical model for measurement noise in quantum error correction is to randomly flip the binary measurement outcome. In experiments, measurements yield much richer information - e.g., continuous current values, discrete photon counts - which is then mapped into binary outcomes by discarding some of this information. In this work, we consider methods to incorporate all of this richer information, typically called soft information, into the decoding of quantum error correcting codes, and in particular the surface code. We describe how to modify both the Minimum Weight Perfect Matching and Union-Find decoders to leverage soft information, and demonstrate these soft decoders outperform the standard (hard) decoders that can only access the binary measurement outcomes. We also introduce a soft measurement error model with amplitude damping, in which measurement time leads to a trade-off between measurement resolution and additional disturbance of the qubits. Under this model we observe that the performance of the surface code is very sensitive to the choice of the measurement time - for a distance-19 surface code, a five-fold increase in measurement time can lead to a thousand-fold increase in logical error rate. Moreover, the measurement time that minimizes the physical error rate is distinct from the one that minimizes the logical performance, pointing to the benefits of jointly optimizing the physical and quantum error correction layers. |
| 11:30am-11:50am | Ciaran Ryan-Anderson, Honeywell Realization of real-time fault-tolerant quantum error correction | Abstract Correcting errors in real-time is essential for reliable large-scale quantum computations. Realizing this high-level function requires a system capable of several low-level primitives, including single-qubit and two-qubit operations, mid-circuit measurements of subsets of qubits, real-time processing of measurement outcomes, and the ability to condition subsequent gate operations on those measurements. In this work, we use a ten qubit QCCD (quantum charge-coupled device) trapped-ion quantum computer to encode a single logical qubit using the $$[[7,1,3]]$$ color code, first proposed by Steane. The logical qubit is initialized into the eigenstates of three mutually unbiased bases using an encoding circuit, and we measure an average logical SPAM error of $$1.7(2) \times 10^{-3}$$ compared to the average physical SPAM error $$2.4(4) \times 10^{-3}$$ of our qubits. We then perform multiple syndrome measurements on the encoded qubit, using a real-time decoder to determine any necessary corrections that are done either as software updates to the Pauli frame or as physically applied gates. Moreover, these procedures are done repeatedly while maintaining coherence, demonstrating a dynamically protected logical qubit memory. Additionally, we demonstrate non-Clifford qubit operations by encoding a magic state with an error rate below the threshold required for magic state distillation. Finally, we present system-level simulations that allow us to identify key hardware upgrades. |
- Home
- Program
- Guide for Gather.Town
- Instructions for Presenters
- Submit Your Abstract
- Code of Conduct
- Subscribe to the SQuInT Mailing List
- Past SQuInT Meetings
SQuInT Chief Organizer
Akimasa Miyake, Associate Professor
amiyake@unm.edu
SQuInT Co-Organizer
Brian Smith, Associate Professor
bjsmith@uoregon.edu
SQuInT Local Organizers
Philip Blocher, Postdoc
Pablo Poggi, Research Assistant Professor
Tzula Propp, Postdoc
Jun Takahashi, Postdoc
Cunlu Zhou, Postdoc
SQuInT Founder
Ivan Deutsch, Regents' Professor, CQuIC Director
ideutsch@unm.edu
