CMOS-based cryogenic control of silicon quantum circuits (2009.14185v1)

Abstract: 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.

• The paper demonstrates a CMOS-based cryogenic control chip that operates silicon qubits at temperatures down to 20mK, achieving 99.99% fidelity.
• The integration of control electronics near quantum chips reduces interconnect complexity, paving the way for scalable quantum processor architectures.
• The controller, operating between 2 and 20 GHz using Intel's 22nm FinFET technology, effectively executes quantum algorithms like Deutsch-Jozsa while maintaining low noise levels.

CMOS-based Cryogenic Control of Silicon Quantum Circuits

The paper "CMOS-based Cryogenic Control of Silicon Quantum Circuits" presents advancements in the integration of cryogenic complementary metal-oxide-semiconductor (CMOS) technology with silicon-based quantum computing devices. This work focuses on addressing the interconnect complexity barrier inherent in scaling quantum processors to host millions of qubits, a requirement for practical quantum computation.

Overview

This research introduces a cryogenic CMOS control chip operational at 3K, designed to drive silicon quantum bits (qubits) at temperatures down to 20mK. The chip's capability to achieve and maintain high fidelity in qubit operations—up to 99.99% assuming ideal conditions—is a significant contribution. This fidelity is crucial for the reliable performance of quantum computation. The CMOS control chip supports microwave burst outputs tailored for silicon spin qubits, aligning well with industry standards for commercial instruments without loss in operational fidelity.

Key Contributions

1. Cryogenic Control Architecture: The paper outlines a cryogenic-compatible control architecture using CMOS technology, essential for overcoming the thermal challenges when deploying control electronics near qubits cooled to milli-Kelvin temperatures. The control chip, developed using Intel's 22nm FinFET technology, operates effectively at frequencies between 2 to 20 GHz, demonstrating compatibility with both spin and superconducting qubits.
2. Integration Potential: By positioning control electronics closer to quantum chips, the research addresses current limitations in quantum interconnects—specifically the extensive number of coaxial control lines currently required. This potential for integration supports scalability in quantum systems.
3. Programmatic Flexibility: The versatility of the control chip was demonstrated through several quantum algorithms, including the Deutsch-Josza algorithm, executed with a two-qubit quantum processor. The cryogenic controller's ability to manage complex pulse sequences and generate precise waveform shapes is integral to efficient quantum information processing.

Testing and Results

The authors rigorously benchmarked the cryogenic controller, demonstrating its equivalent performance to room-temperature counterparts, such as standard arbitrary waveform generators and vector signal generators. Continuous wave outputs and advanced spectrum analysis reveal the controller's spurious-free dynamic range (SFDR) of 46 dB and signal-to-noise ratio (SNR) of 48 dB. The device's output was characterized without impacting the electron temperature of quantum dots, crucial for maintaining coherent qubit operations.

Implications for Quantum Computing

The integration of cryogenic CMOS circuits signifies an essential step toward fully packaged and scalable quantum computing platforms. By addressing the heat dissipation constraints and introducing methods for close integration, this research suggests tangible pathways for developing large-scale quantum computers. Future work might focus on optimizing power consumption further, enabling operation at temperatures as low as 1K or integrating quantum processors and controllers on the same die through technologies like flip-chip bonding.

This paper highlights the synergy between advanced CMOS technology and quantum computing, suggesting that continued integration efforts will be vital in resolving existing roadblocks in quantum scalability. These contributions spur a promising direction for the quantum computing field, emphasizing a blended approach of classical and quantum technologies to enhance computational power and efficiency.