Quantum Computing
Quantum computing is quickly emerging as a solution to address the high-speed and high data rate demands in a number of use cases. It is being designed into next-generation GPS systems, MRI machines, semiconductors, and lasers, amongst others.
Because of this promise, governments throughout the world are investing billions in R&D for quantum computing. In the United States, the National Quantum Initiative (NQI) Act allows federal government agencies to collaborate with academia and private industry to accelerate the growth of quantum technologies. The CHIPS and Science Act of 2022 amended the NQI Act to authorize R&D in quantum networking infrastructure, standards development, and other initiatives.
Benefits of Qubits
Similar to traditional computers, quantum computing use digital bits. The notable difference is the building block. Quantum computing uses quantum bits, commonly referred to as qubits. Unlike legacy digital bits that are either a 0 or 1, qubits can simultaneously be a 0 and 1.
In a quantum computing environment, a qubit control system is connected to the processor through numerous RF cables. Several cables are necessary per qubit for control and readout. As a reference, a 50-qubit system requires more than 120 cables. Understanding the behavior of control pulses as they propagate through cables, as well as RF amplifiers, filters, and attenuators, is essential to achieve the necessary pulse and maintain the required qubit fidelity.
A typical qubit lifetime is approximately 100 us. To support this, the feedback loop must operate with low latency of typically < 1 us from readout to qubit control. Each instrument and/or function block in the loop must operate as fast as possible to support such operation.
The quantum processor is located at the bottom of a cryostat, at temperatures as low as 10 mK. One challenge of this configuration is ensuring connectivity to the chip while minimizing crosstalk and other errors. To address these concerns, quantum computing designs include attenuators and filters at different temperature stages of the cryostat to minimize the heat through the cables and to reduce noise.
The cryostat RF paths often also include amplifiers and circulators, to improve the signal-to-noise ratio (SNR) and to shorten measurement times. All these RF components and paths must be calibrated to optimize SNR, phase noise, and latency.
Quantum Computing Testing Configurations
One key issue is systematic errors, which can be accurately measured using advanced vector network analyzers (VNA) and error correction calibrations. Given the high number of RF channels in a typical quantum setup, a multiport or modular VNA is ideal to optimize the calibration.
Because qubits are stimulated by microwave pulses in the 2 GHz to 40 GHz range, up-converters and down-converters are usually involved to conduct the qubit control. Signal generators with high output signal purity are a measuring solution, as they act as local oscillators (LO) for up- and down-conversion stages or to drive the amplifiers in the chain. Wideband and real-time spectrum analyzers, as well as phase noise analyzers, are used to characterize the quality of generated signals.
Anritsu has a comprehensive offering of RF and microwave solutions dedicated to quantum computing - from qubits design to final deployment. With a complete set of RF and microwave quantum computing solutions, Anritsu allows scientists to maximize SNR by enhancing spectral purity and minimizing phase-noise, shortening measurement times by reducing latency and switching.
