18 research outputs found
Probing single electrons across 300 mm spin qubit wafers
Building a fault-tolerant quantum computer will require vast numbers of
physical qubits. For qubit technologies based on solid state electronic
devices, integrating millions of qubits in a single processor will require
device fabrication to reach a scale comparable to that of the modern CMOS
industry. Equally importantly, the scale of cryogenic device testing must keep
pace to enable efficient device screening and to improve statistical metrics
like qubit yield and process variation. Spin qubits have shown impressive
control fidelities but have historically been challenged by yield and process
variation. In this work, we present a testing process using a cryogenic 300 mm
wafer prober to collect high-volume data on the performance of
industry-manufactured spin qubit devices at 1.6 K. This testing method provides
fast feedback to enable optimization of the CMOS-compatible fabrication
process, leading to high yield and low process variation. Using this system, we
automate measurements of the operating point of spin qubits and probe the
transitions of single electrons across full wafers. We analyze the random
variation in single-electron operating voltages and find that this fabrication
process leads to low levels of disorder at the 300 mm scale. Together these
results demonstrate the advances that can be achieved through the application
of CMOS industry techniques to the fabrication and measurement of spin qubits.Comment: 15 pages, 4 figures, 7 extended data figure
CMOS-based cryogenic control of silicon quantum circuits
The most promising quantum algorithms require quantum processors hosting
millions of quantum bits when targeting practical applications. A major
challenge towards large-scale quantum computation is the interconnect
complexity. In current solid-state qubit implementations, a major bottleneck
appears between the quantum chip in a dilution refrigerator and the room
temperature electronics. Advanced lithography supports the fabrication of both
CMOS control electronics and qubits in silicon. When the electronics are
designed to operate at cryogenic temperatures, it can ultimately be integrated
with the qubits on the same die or package, overcoming the wiring bottleneck.
Here we report a cryogenic CMOS control chip operating at 3K, which outputs
tailored microwave bursts to drive silicon quantum bits cooled to 20mK. We
first benchmark the control chip and find electrical performance consistent
with 99.99% fidelity qubit operations, assuming ideal qubits. Next, we use it
to coherently control actual silicon spin qubits and find that the cryogenic
control chip achieves the same fidelity as commercial instruments. Furthermore,
we highlight the extensive capabilities of the control chip by programming a
number of benchmarking protocols as well as the Deutsch-Josza algorithm on a
two-qubit quantum processor. These results open up the path towards a fully
integrated, scalable silicon-based quantum computer
Sex difference and intra-operative tidal volume: Insights from the LAS VEGAS study
BACKGROUND: One key element of lung-protective ventilation is the use of a low tidal volume (VT). A sex difference in use of low tidal volume ventilation (LTVV) has been described in critically ill ICU patients.OBJECTIVES: The aim of this study was to determine whether a sex difference in use of LTVV also exists in operating room patients, and if present what factors drive this difference.DESIGN, PATIENTS AND SETTING: This is a posthoc analysis of LAS VEGAS, a 1-week worldwide observational study in adults requiring intra-operative ventilation during general anaesthesia for surgery in 146 hospitals in 29 countries.MAIN OUTCOME MEASURES: Women and men were compared with respect to use of LTVV, defined as VT of 8 ml kg-1 or less predicted bodyweight (PBW). A VT was deemed 'default' if the set VT was a round number. A mediation analysis assessed which factors may explain the sex difference in use of LTVV during intra-operative ventilation.RESULTS: This analysis includes 9864 patients, of whom 5425 (55%) were women. A default VT was often set, both in women and men; mode VT was 500 ml. Median [IQR] VT was higher in women than in men (8.6 [7.7 to 9.6] vs. 7.6 [6.8 to 8.4] ml kg-1 PBW, P < 0.001). Compared with men, women were twice as likely not to receive LTVV [68.8 vs. 36.0%; relative risk ratio 2.1 (95% CI 1.9 to 2.1), P < 0.001]. In the mediation analysis, patients' height and actual body weight (ABW) explained 81 and 18% of the sex difference in use of LTVV, respectively; it was not explained by the use of a default VT.CONCLUSION: In this worldwide cohort of patients receiving intra-operative ventilation during general anaesthesia for surgery, women received a higher VT than men during intra-operative ventilation. The risk for a female not to receive LTVV during surgery was double that of males. Height and ABW were the two mediators of the sex difference in use of LTVV.TRIAL REGISTRATION: The study was registered at Clinicaltrials.gov, NCT01601223
Designing a DDS-Based SoC for High-Fidelity Multi-Qubit Control
The design of a large-scale quantum computer requires co-optimization of both the quantum bits (qubits) and their control electronics. This work presents the first systematic design of such a controller to simultaneously and accurately manipulate the states of multiple spin qubits or transmons. By employing both analytical and simulation techniques, the detailed electrical specifications of the controller have been derived for a single-qubit gate fidelity of 99.99% and validated using a qubit Hamiltonian simulator. Trade-offs between several architectures with different levels of digitization are discussed, resulting in the selection of a highly digital DDS-based solution. Initiating from the system specifications, a complete error budget for the various analog and digital circuit blocks is drafted and their detailed electrical specifications, such as signal power, linearity, spurs and noise, are derived to obtain a digital-intensive power-optimized multi-qubit controller. A power consumption estimate demonstrates the feasibility of such a system in a nanometer CMOS technology node. Finally, application examples, including qubit calibration and multi-qubit excitation, are simulated with the proposed controller to demonstrate its efficacy. The proposed methodology, and more specifically, the proposed error budget lay the foundations for the design of a scalable electronic controller enabling large-scale quantum computers with practical applications. (OLD)Applied Quantum ArchitecturesOLD QCD/Charbon LabQuTechElectronic
Cryogenic CMOS for Qubit Control and Readout
Quantum computers have been heralded as a novel paradigm for the solution of today's intractable problems, whereas the core principles of quantum computation are superposition, entanglement and interference, three fundamental properties of quantum mechanics [1]. A quantum computer generally comprises a quantum processor, made of an array of quantum bits or qubits, and a classical controller, which is used to control and read out the qubits. Quantum algorithms are generally mapped onto a circuit of quantum gates that operate on multiple qubits. Unlike conventional digital bits, qubits can take a coherent state ranging from |0〉 to |1〉 on a continuous sphere, known as the Bloch Sphere and they are implemented based on several mechanisms. While many solid-state implementations of qubits exist, an exhaustive description of available technologies is beyond the scope of this paper [2] [3].Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.QCD/Vandersypen LabQN/Vandersypen LabElectronicsQuantum Circuit Architectures and Technolog
A Scalable Cryo-CMOS Controller for the Wideband Frequency-Multiplexed Control of Spin Qubits and Transmons
Building a large-scale quantum computer requires the co-optimization of both the quantum bits (qubits) and their control electronics. By operating the CMOS control circuits at cryogenic temperatures (cryo-CMOS), and hence in close proximity to the cryogenic solid-state qubits, a compact quantum-computing system can be achieved, thus promising scalability to the large number of qubits required in a practical application. This work presents a cryo-CMOS microwave signal generator for frequency-multiplexed control of 4 x 32 qubits (32 qubits per RF output). A digitally intensive architecture offering full programmability of phase, amplitude, and frequency of the output microwave pulses and a wideband RF front end operating from 2 to 20 GHz allow targeting both spin qubits and transmons. The controller comprises a qubit-phase-tracking direct digital synthesis (DDS) back end for coherent qubit control and a single-sideband (SSB) RF front end optimized for minimum leakage between the qubit channels. Fabricated in Intel 22-nm FinFET technology, it achieves a 48-dB SNR and 45-dB spurious-free dynamic range (SFDR) in a 1-GHz data bandwidth when operating at 3 K, thus enabling high-fidelity qubit control. By exploiting the on-chip 4096-instruction memory, the capability to translate quantum algorithms to microwave signals has been demonstrated by coherently controlling a spin qubit at both 14 and 18 GHz