A team of researchers from the University of New South Wales (UNSW) in Sydney Achieving a breakthrough in spin qubit coherence time (opens in new tab)The study drew on the team’s previous work on so-called “dressed” qubits. This means that qubits are always under the influence of electromagnetic fields and protected from interference.In addition, researchers New design protocol, SMART, (opens in new tab) We take advantage of the increased coherence time so that individual qubits can be safely steered to perform the required computations.
This improvement allowed researchers to record coherence times up to 2 ms. This puts him more than 100 times higher than similar control methods in the past, but still far from the time it takes for an eyelid to blink.
There are several ways to increase the computational power available in quantum systems (opens in new tab)Increasing the number of qubits can be thought of as analogous to a classical transistor, but one of them. In addition to increasing the number of addressable qubits in a given system, it is also important whether these qubits provide correct results (several error correction implementations are under development). Yet another way to improve performance is to increase the number of times a qubit can hold information before decoherence. This is the moment when the qubit’s state collapses and all the information it contains is lost. For spin qubits, the death knell of the qubit state rings every time an electron stops spinning.
“Long coherence time means longer time to store quantum information, which is exactly what we need when doing quantum manipulation,” he said. Her student, Amanda Seedhouse, contributed her work to theoretical quantum computing research. “Coherence time basically tells you how long you can do all the operations in an algorithm or sequence you want to do before you lose all the information in the qubit,” she continued Amanda.
The researchers’ SMART (Sinusoidally Modulated, Always Rotating and Tailored) protocol aims to improve coherence times by reducing the interference introduced into the qubit environment while allowing fine-grained control over each qubit. increase.
One way to interact with silicon spin qubits is to expose them to microwave fields, but this has proven to be a taxing method. However, maintaining so many microwave-based magnetic fields at work in the quantum realm, in addition to scaling energy consumption and increasing heat dissipation from a large number of antennas, increases environmental noise. Also, the higher the environmental noise, the more likely qubit decoherence will occur. Additionally, scientists’ attempts to increase control over qubit states have gone against coherence time.
All of this is prohibitive for the requirements of full-scale quantum computing, which is expected to require millions of qubits working in unison towards the ultimate computational goal.
Researchers use dielectric resonators to that a single antenna could be used instead to control the entire qubit field (opens in new tab)Antennas, which are expected to handle millions of qubits simultaneously, work by keeping electrons spin. This is the quantum property that makes silicon qubits part of their appeal. Another factor is that silicon qubits can ultimately leverage the decades of expertise of silicon manufacturers to deliver the best performance and highest manufacturing yields of this material.
But while it is essential, maintain the spin state across the qubit field (opens in new tab) (To prevent decoherence), qubits must be manipulated individually for accurate computation. For example, if changes in the microwave field affect all qubits similarly, we have little control over the information each spin qubit represents.
Researchers devised and adopted the SMART protocol to more easily interact with qubit states. Through it, they could manipulate the spin cubits to rock back and forth rather than spinning in a circle. Each qubit was made to move back and forth, like the pendulum in Grandpa’s clock. By interacting with each qubit’s swing via an electric field, the qubits were pulled out of resonance while maintaining rhythm, allowing researchers to make them swing at different tempos compared to neighboring qubits ( One was “rising” and the other was “falling”). ”).
“Think of it like two kids on a swing going forward and backward in sync,” says Seedhouse. “Pressing either can cause it to reach the opposite end of the arc, so when one goes to 1, the other can go to 0.”
The efforts of UNSW researchers have shown that groups of qubits can be controlled via a single microwave-based magnetic source. In contrast, applying an electronically controlled magnetic field allows better control of individual qubits. According to the researchers, the SMART protocol leverages potential pathways for full-scale quantum computers.
“We showed a simple and elegant way to control all qubits at once, which also improves performance,” he said. Dr. Henry Yang (opens in new tab)one of the senior researchers on the team.
