Mitigating signal interferences in quantum computing applications

Multi-tone microwave signals are composed of a series of sine waves, each wave displaying a distinct frequency and amplitude. As these signals include many different frequencies, they can be used to manipulate qubits, the fundamental units of quantum computing, to enable advanced computation and simulations.

The periodicity of microwave frequencies, however, can lead to interferences, which amplify voltage peaks and exceed the output range of qubit controllers employing arbitrary waveform generators (AWGs). The achievable levels of quantum operation are thus limited to the AWG’s operational range.

To ensure the precision of signals, Ohira et al. explored the use of a crest factor reduction algorithm in suppressing voltage peaks of multi-tone microwave signal interferences.

“The proposed method not only enables frequency-multiplexed qubit control but also allows for simultaneous two-qubit gate operation,” said author Ryutaro Ohira. “This capability enhances the efficiency and scalability of quantum computing systems, making it a key advancement in the field.”

The authors found that the algorithm successfully mitigates the effect of signal interferences, reducing the amplitude of a 30-frequency-multiplexed signal to less than one-tenth that of a single-tone microwave signal. Furthermore, the effect of peak suppression is enhanced along with an increase in frequency components, highlighting the algorithm’s potential applications in frequency-multiplexed qubit control and simultaneous two-qubit gate operation.

Building on their discovery, the authors plan to validate their theoretical approaches with experimentation involving quantum computers.

“Our study potentially provides a route for realizing large-scale quantum computers based on frequency multiplexing,” said Ohira. “The next step involves experimentally demonstrating the proposed method, which is essential for proving the method’s practical applicability.”

Source: “Optimizing multi-tone microwave pulses via phase selection for quantum computing applications,” by R. Ohira, R. Matsuda, H. Shiomi, K. Ogawa, and M. Negoro, Journal of Applied Physics (2024). The article can be accessed at https://doi.org/10.1063/5.0222724 .