Hardware-efficient quantum error correction using concatenated bosonic qubits
To solve problems of practical importance, quantum computers will likely need to incorporate quantum error correction, where a logical qubit is redundantly encoded in many noisy physical qubits. The large physical-qubit overhead typically associated with error correction motivates the search for more hardware-efficient approaches. To this end, in this talk I will describe our recent superconducting circuit experiment realizing a logical qubit memory via the concatenation of encoded bosonic cat qubits with an outer repetition code.
A Landau Level at Zero Flux, Magic, and Abelianization
A Landau level (which is a flat band) forms only when a magnetic flux with non-zero total flux threads a system. In fact the degeneracy at the flat band is proportional to the flux. So no flat band can form when the magnetic flux averages to zero. We will discuss this and then show otherwise. This is relevant to time reversal symmetric systems that form flat bands such as magic-angle twisted bilayer graphene. In this talk the magic behind those systems will be revealed through the simplest model that gives rise to magical behaviour.
Building Topological Quantum Matter in Superconducting Wire Arrays
We utilize a notion of "combinatorial gauge symmetry", where the gauge symmetry involves not just local rotations of spins, but also permutations of spins. This allows the construction of exact gauge invariant Hamiltonians using just two-body interactions. Models constructed in this way include the toric code and any Abelian and Non-Abelian generalization. New models also emerge in this paradigm. An advantage of the exact symmetry: the topological energy gaps need not be limited to a perturbative regime, but could potentially persist for a wider range of parameters.
Quantum Routing and Entanglement Capacity Through Bottlenecks
To implement arbitrary quantum interactions in architectures with restricted topologies, one may simulate all-to-all connectivity by routing quantum information. Therefore, it is of natural interest to find optimal protocols and lower bounds for routing. We consider a connectivity graph, G, of 2 regions connected only through an intermediate region of a small number of qubits that form a vertex bottleneck. Existing results only imply a trivial lower bound on the entangling rate and routing time across a vertex bottleneck.
Exponentially Reduced Circuit Depths Using Trotter Error Mitigation
Abstract: Product formulae are a popular class of digital quantum simulation algorithms due to their conceptual simplicity, low overhead, and performance which often exceeds theoretical expectations. Recently, Richardson extrapolation and polynomial interpolation have been proposed to mitigate the Trotter error incurred by use of these formulae. This work provides an improved, rigorous analysis of these techniques for the task of calculating time-evolved expectation values.
Fiber Bundle Fault Tolerance of GKP Codes
Fault tolerance is a notion of fundamental importance to the field of quantum information processing. It is one of the central properties a quantum computer must possess in order to enable the achievement of large scale practical quantum computation. While a widely used, general, and intuitive concept, within the literature the term fault tolerant is often applied to specific procedures in an ad-hoc fashion tailored to details of the context or platform under discussion.
New Design Packs Two Qubits into One Superconducting Junction
Quantum computers are potentially revolutionary devices and the basis of a growing industry. However, their technology isn’t standardized yet, and researchers are still studying the physics behind the diverse ways to build these quantum devices. Even the most basic building blocks of a quantum computer—qubits—are still an active research topic.