RQS

Circuit QED enables the combined use of qubits and oscillator modes. Despite a variety of available gate sets, many hybrid qubit-boson (i.e., oscillator) operations are realizable only through optimal control theory (OCT) which is oftentimes intractable and uninterpretable. We introduce an analytic approach with rigorously proven error bounds for realizing specific classes of operations via two matrix product formulas commonly used in Hamiltonian simulation, the Lie–Trotter and Baker–Campbell–Hausdorff product formulas.

Hamiltonian simulation is one of the most promising applications of quantum computing. Recent experimental results suggest that continuous-time analog quantum simulation would be advantageous over gate-based digital quantum simulation in the Noisy Intermediate-Size Quantum (NISQ) machine era. However, programming such analog quantum simulators is much more challenging due to the lack of a unified interface between hardware and software, and the only few known examples are all hardware-specific.

Intermediate-scale quantum devices are becoming more reliable, and may soon be harnessed to solve useful computational tasks. At the same time, common classical methods used to verify their computational output become intractable due to their prohibitive scaling of required resources with system size. In this talk, I aim at giving an overview of selected verification strategies. Inspired by recent experimental progress, we analyze efficient cross-platform verification protocols for quantum states and computations.

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.

Trapped atomic ions are a highly versatile platform for quantum simulation and computation. In this talk, I will provide a brief description of the quantum control that enables both analog and digital modes of quantum simulation on this platform before reporting on two recent results: a digital quantum simulation that measured the first out-of-time-order correlators in a thermal system, and an analog simulation of particles with exotic statistics.

In recent years, there have been rapid breakthroughs in quantum technologies that offer new opportunities for advancing the understanding of basic quantum phenomena; realizing novel strongly correlated systems; and enhancing applications in quantum communication, computation, and sensing. Cutting edge quantum technologies simultaneously require high fidelity quantum-limited measurements and control.