Quantum computers work with qubits. The latter, as it turned out, are capable of changing productivity — they are degrading. Scientists have found a way to track these fluctuations online. The process takes milliseconds. The discovery opens the way to improved reliability. Qubits, xrust writes, are the fundamental units of quantum computers that scientists hope will one day outperform the most powerful modern machines. But qubits are extremely sensitive. The materials used to create them often contain tiny defects that scientists still don't fully understand. These microscopic imperfections can change their position hundreds of times per second. At the same time, they change the rate of energy loss by the qubit, and with it valuable quantum information.
Until recently, standard testing methods took up to a minute to measure the performance of a qubit. This was too little to detect these rapid fluctuations. Instead, the researchers could only determine the average rate of energy loss, which obscured the true and often unstable behavior of the qubit.
Real-time qubit control using FPGA
The research team, writes sciencedaily, has developed an adaptive real-time measurement system that monitors changes in the rate of energy loss (relaxation) of a qubit as they occur.
The new approach is based on a fast classical controller that updates its estimate of the qubit's relaxation rate within milliseconds. This matches the natural speed of the fluctuations themselves, rather than being delayed by seconds or minutes, as was the case with older methods.
To achieve this goal, the team used a field-programmable gate array (FPGA), a type of classic processor designed for extremely fast operations. By running the experiment directly on the FPGA, they were able to quickly get a “rough estimate” of the rate of energy loss of a qubit using just a few measurements. This eliminated the need for slower data transfer to a conventional computer.
Programming an FPGA for such specialized tasks can be challenging. However, the researchers were able to update the internal Bayesian model of the controller after each qubit measurement. This allowed the system to continually refine its understanding of the qubit's state in real time.
As a result, the controller now keeps up with changes in the qubit’s environment. The measurements and adjustments occur on virtually the same time scale as the fluctuations themselves, making the system about a hundred times faster than previously demonstrated.
This work also revealed something new. Previously, scientists did not know how quickly fluctuations occur in superconducting qubits. Now these experiments have provided insight into this.
Commercial quantum equipment and advanced control technologies
class=»notranslate»>__GTAG5__ FPGAs (programmable logic integrated circuits) have long been used in other areas of science and technology. In this case, the researchers used a commercially available FPGA controller from Quantum Machines called the OPX1000. The system can be programmed in a language similar to Python, which many physicists already use, making it more accessible to research groups around the world.
Why real-time calibration is important for quantum computers
class=»notranslate»>__GTAG11__ Quantum technologies promise powerful new capabilities, although the development of large-scale quantum computers for practical applications is still ongoing. Progress often occurs gradually, but sometimes there are significant steps forward.
The results obtained change the way scientists think about testing and calibrating superconducting quantum processors. With modern materials and manufacturing methods, a shift to real-time monitoring and adjustment appears necessary to improve reliability. The results also highlight the importance of partnerships between academic research and industry, and the creative use of available technologies.
Xrust Quantum computers: qubits are subject to fluctuations
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