RQS

Noise is widely regarded as a major obstacle to quantum computing. Fortunately, this problem can be solved efficiently due to the existence of the threshold theorem. It states that under sufficiently weak noise and universal assumptions, there always exists an active quantum error correction protocol with only logarithmic hardware overhead. One may ask: can a similar result be obtained for autonomous (passive) error correction, where noise is suppressed by natural or engineered dissipation?

Noncommuting conserved quantities have recently launched a subfield of quantum thermodynamics. In conventional thermodynamics, a system of interest and an environment exchange quantities—energy, particles, electric charge, etc.—that are globally conserved and are represented by Hermitian operators. These operators were implicitly assumed to commute with each other, until a few years ago. Freeing the operators to fail to commute has enabled many theoretical discoveries—about reference frames, entropy production, resource-theory models, etc.

The demands of fault tolerance mean that a wide variety of simple and exotic noise types must be tamed for quantum devices to progress. Crucially, this means keeping up with complex correlated — or non-Markovian — effects, both with respect to the background process and to control operations. Recently, we have developed a generalised version of quantum process tomography to characterise arbitrary non-Markovian processes in practice.

Suppressing errors is the central challenge for quantum computers to become practically relevant. The paradigmatic approach to this is quantum error correction, which uses quantum codes—redundantly encoded ‘logical qubits’—in combination with repeated rounds of error detection and correction. In this work, we report the realization of a quantum processor whose fundamental processing units are such logical qubits. The processor is based on reconfigurable arrays of neutral atoms in optical tweezers.

RQS presents a panel discussion with RQS students who have recently interned at a company. They will discuss:

• What they did during their internship
• How they learned about/applied for the internship
• Things they wish they had known in advance and advice for other applicants
• How RQS and/or an RQS university could make the internship process easier and better

They will also answer your questions if you have an interest in a future internship.

How to write successful grant proposals, pushing your writing skills to the next level. Erin will provide a general overview of grant writing and focus on proposals for education and outreach, a key mandate of the NSF grant for the Quantum Leap Challenge Institute for Robust Quantum Simulation.

Please prepare your questions in advance and send them to rqs-seed@umiacs.umd.edu.

How to write successful grant proposals, pushing your writing skills to the next level. Mohammad will provide a general overview of grant writing and focus on research proposals. Come with your general, and/or specific questions. Send them to rqs-seed@umiacs.umd.edu or bring them to the meeting.

You can send your questions in advance to rqs-seed@umiacs.umd.edu.

Randomized benchmarking protocols have become the prominent tool for assessing the quality of gates on digital quantum computing platforms.  In `classical’ variants of randomized benchmarking multi-qubit gates are drawn uniformly from a finite group.  The functioning of such schemes be rigorous guaranteed under realistic assumptions.  In contrast, experimentally attractive and practically more scalable randomized benchmarking schemes often directly perform random circuits or use other non-uniform probability measures.

Nuclear magnetic resonance (NMR) spectroscopy is a useful tool in understanding molecular composition and dynamics, but simulating NMR spectra of large molecules becomes intractable on classical computers as the spin correlations in these systems can grow exponentially with molecule size. In contrast, quantum computers are well suited to simulate NMR spectra of molecules, particularly zero- to ultralow field (ZULF) NMR where the spin-spin interactions in the molecules dominate.

Quantum computers in the NISQ era are prone to noise. A range of quantum error mitigation techniques has been proposed to address this issue. Zero-noise extrapolation (ZNE) stands out as a promising one. ZNE involves increasing the noise levels in a circuit and then using extrapolation to infer the zero noise case from the noisy results obtained. This paper presents a novel ZNE approach that does not require circuit folding or noise scaling to mitigate depolarizing and/or decoherence noise.