Accelerating quantum computer developments

Product development: Given the recent breakthroughs in quantum technology development in R&D labs all over the world, the perspective of high-tech companies has changed. Product development is initiated next to the existing research and technology development activities. Quantum computer product roadmap: Considering the quantum computer as a product requires standardization and integration of all its building blocks and a mature supply chain that can provide high-quality components and can ensure the security of supply. The product development approach puts focus on the functionality and performance requirements of the product and uses state-of-the-art technology to build the product. Based on the expected requirements of future products it is possible to outline a product development roadmap. Quantum computer product roadmap: It is expected that a fully functional quantum computer will be available within a decade from now, and will be used by the High Performance Computing (HPC) market, where it will replace (part of) the supercomputers that are currently used for complex calculations and data management. In the short term, a partly functional quantum computer will be available and of interest to the R&D market, which has a need for such a product to expedite their quantum technology developments. ImpaQT project: In this paper, we present the product development approach and roadmap for quantum computers, based on superconducting circuits as an example. A group of companies in the Dutch quantum ecosystem (Quantum Delta) have joined forces and have started the ImpaQT project. The companies of the ImpaQT consortium form a local supply chain for key components of quantum computers.

APS March Meeting 2021: Scientific Talk R33

A low-noise, flexible and scalable control paradigm for quantum computing in the NISQ era.

Abstract: In the race towards quantum computers with real-life applications, major challenges have to be overcome. We battle these challenges by providing hardware stacks that combine low noise and drift, a novel distributed instruction set architecture (ISA) and a scalable infrastructure for low-latency feedback. This creates a system with wide applications in quantum computing and opens up new avenues in quantum error correction.

APS March Meeting 2021: Scientific Talk M34

Quantify: An open-source framework for operating quantum computers in the NISQ era.

Abstract: Operating a quantum computer in the NISQ era is an often-underestimated challenge. Specifically, the tune-up and execution of quantum algorithms. Here, we present Quantify, a robust and extensively documented open-source experiment platform. Quantify contains all the basic functionality to control experiments, as well as a novel scheduler featuring a unique hybrid control model allowing quantum gate- and pulse-level descriptions to be combined in a clearly defined and hardware-agnostic way. This opens up new avenues for the efficient execution of calibration routines as well as variational quantum algorithms (VQA).

APS March Meeting 2021: Technical Demo + Q&A

Qblox & Quantify: Fully integrated control hardware and open-source software for a variety of scalable quantum computers

Abstract: Meet the Qblox control stack: commercially available, massively scalable control systems that generate and interpret signals in the range from DC to 18.5 GHz. By giving our sequencers real-time access to pulse amplitudes, offsets and modulation phases, this allows bypassing slow communication with the user PC. The Qblox hardware can be conveniently operated with Quantify. This creates a massively scalable control stack with tight integration of all hardware and software components applicable to a variety of quantum systems.

Publication - Science Advances

Protecting quantum entanglement from qubit errors and leakage via repetitive parity measurements

Protecting quantum information from errors is essential for large-scale quantum computation. Quantum error correction (QEC) encodes information in entangled states of many qubits, and performs parity measurements to identify errors without destroying the encoded information. However, traditional QEC cannot handle leakage from the qubit computational space. Leakage affects leading experimental platforms, based on trapped ions and superconducting circuits, which use effective qubits within many-level physical systems. We investigate how two-transmon entangled states evolve under repeated parity measurements, and demonstrate the use of hidden Markov models to detect leakage using only the record of parity measurement outcomes required for QEC. We show the stabilization of Bell states over up to 26 parity measurements by mitigating leakage using postselection, and correcting qubit errors using Pauli-frame transformations. Our leakage identification method is computationally efficient and thus compatible with real-time leakage tracking and correction in larger quantum processors.

Publication - Physical Review Applied

Active resonator reset in the nonlinear dispersive regime of circuit QED

We present two pulse schemes for actively depleting measurement photons from a readout resonator in the nonlinear dispersive regime of circuit QED. One method uses digital feedback conditioned on the measurement outcome while the other is unconditional. In the absence of analytic forms and symmetries to exploit in this nonlinear regime, the depletion pulses are numerically optimized using the Powell method. We shorten the photon depletion time by more than six inverse resonator linewidths compared to passive depletion by waiting. We quantify the benefit by emulating an ancilla qubit performing repeated quantum parity checks in a repetition code. Fast depletion increases the mean number of cycles to a spurious error detection event from order 1 to 75 at a 1 μs cycle time.