Multiple Qubits should be manipulated to perform practical quantum computing, which requires a broad frequency range for the qubit control chip. We present a 4 K cryo-CMOS quantum control chip featuring a Mixing (MIX)/ Non-return-to-zero (NRZ) mode radio frequency digital to analog converter (RF-DAC) and an up-conversion mixer. By opting for Mixing Mode RF-DAC and a mixer for two-stage frequency up-conversion instead of direct-conversion or other methods, our controller can achieve a wider modulated frequency range and lower power consumption.
Multiple Qubits should be manipulated to perform practical quantum computing, which requires a broad frequency range for the qubit control chip. We present a 4 K cryo-CMOS quantum control chip featuring a Mixing (MIX)/ Non-return-to-zero (NRZ) mode radio frequency digital to analog converter (RF-DAC) and an up-conversion mixer. By opting for Mixing Mode RF-DAC and a mixer for two-stage frequency up-conversion instead of direct-conversion or other methods, our controller can achieve a wider modulated frequency range and lower power consumption.
This article presents a 4 K cryo-CMOS RF-DAC based super-heterodyne transmitter for superconducting-qubit control. The transmitter integrates an RF-DAC based XY-path driver for quantum state manipulation and a current-steering DAC based Z-path driver for flux-bias control. To balance wideband frequency coverage and power consumption, the XY path separates programmable intermediate-frequency (IF) waveform synthesis from final microwave frequency translation. A 10-bit dual-mode RF-DAC first generates wide-IF control pulses, followed by a mixer for up-conversion to the qubit-frequency. By digitally selecting the non-return-to-zero (NRZ) or mixing (MIX) mode according to the target IF range, the RF-DAC exploits different Nyquist zones to extend the usable IF range without proportionally increasing the sampling clock frequency, enabling flexible and FDM-compatible qubit manipulation without increasing too much power. To mitigate RF-DAC current-cell mismatches under cryogenic operation, a mean-absolute-error (MAE)-based foreground calibration technique is proposed. The fully integrated controller is fabricated in a 28-nm CMOS process. The prototype is measured with ~1 GHz IF bandwidth and 8 GHz RF bandwidth under 46 mW power dissipation at the 4-K stage, and it achieves an SFDR of 33.24–41.62 dB within the 4–8 GHz. The ASIC is installed in a dilution refrigerator as a replacement of the classical control instrument, the experiment results further verify the functionality of the ASIC.
This article presents a fully integrated Cryo-CMOS system on chip (SoC) for quantum computing. The proposed SoC integrates a radio frequency (RF) pulse modulator for qubit state manipulation, a multi-tone signal generator and a coherent receiver for qubit state readout, and 22 DACs for high-speed voltage pulsing of qubit gates. By adopting frequency division multiplexing and direct digital synthesis (DDS), the RF pulse modulator can control up to 16 qubits over a single RF line, and the readout receiver can detect the state of up to six qubits simultaneously. The proposed SoC also integrates a microcontroller for low latency on-chip signal processing and increased flexibility in implementing quantum instruction sets. A detailed analysis of qubit-state readout fidelity and the impact of finite DAC resolution on two-qubit gate fidelity is also included in this article, together with an electrical specification summary. The SoC is implemented in Intel’s 22 nm FFL fin field-effect transistor (FinFET) process, and it is characterized both at room and 4 K temperatures. The performance of each specific block is measured, with the readout characterized in a loop-back configuration. Generation of the control signals required for a full Rabi oscillation experiment is also demonstrated. This article also describes the cryogenic thermalization techniques used to integrate the SoC in the dilution refrigerator and shows temperature measurements during operation.
This paper presents the design and test results of a CMOS current-based Digital to Analog Converter (DAC) that operates at cryogenic temperatures and that can be used to precisely control the amount of flux coupled to qubits or that can be used in the readout of superconducting circuits. The current pulse output can be controlled in terms of its amplitude, rise and fall slopes, via digital controls, and pulse width, via external triggers, while driving a superconducting circuit. The design has been implemented in a planar 90 nm CMOS process and test results closely match circuit predictions. The solution's wide degree of digital tunability affords potential application of the same device to many types of quantum circuits, beyond those discussed here. Due to the wide-ranging flexibility of digital CMOS control, we envision that this DAC design will enable the next generation of high-fidelity cryo-CMOS control architectures for superconducting qubits.
In today's mainstream superconducting quantum computing platforms in a dilution refrigerator, the qubits work at a cryogenic temperature (CT) of a few tens of mK, while the qubit controller hardware works on plates with temperature ranging from a few K to room temperature (RT). The highly-integrated cryo-CMOS qubit controller ASIC that can fully work at 3-4K has been proven to be the most feasible way to scale down the quantum computing system [1–5]. In [1], a pulse modulator is implemented with a limited qubit driving capability, which can only generate fixed length symmetric driving pulse. The controllers in [2], [3] generated the RF driving pulse with a frequency division multiplexing (FDM) mode, with the power dissipation of 192mW/qubit and 46.5mW/qubit, respectively. In [4], a local oscillator (LO) was included to improve the controller integration level, and the chip power consumption was 24.1mW/qubit. An arbitrary waveform generation (AWG) functionality digital design was presented in [5] with a power consumption of 23.1mW/qubit. Nevertheless, with continuously increasing number of qubits to integrate, it remains as one of the major tasks to further reduce the power consumption and size of controller.
This paper presents a 28 nm cryo-CMOS system-on-chip (SoC) for the dispersive readout of superconducting qubits operating between 6.5-8.1 GHz at 4 K. The SoC includes a quadrature VCO and a full zero-IF transmitter and receiver chain, including 200 MS/s7-bit DACs, ADCs, and digital. It can generate pulses up to 640 ns duration, and it attains a very low-power readout operation (9.8 mW) compared to its counterparts with 0.5-0.6 dB noise figure, 65–89 dB gain, and -71 dBm maximum TX output power at 4 K. Furthermore, with its duty-cycled mode, the SoC reduces the average power dissipation for the readout application.
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 × 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.