Researchers from the US Department of Energy’s (DOE) Argonne National Laboratory and the University of Chicago have reached a new record by holding quantum bits (qubits) in a coherent quantum state for more than five seconds. The research, published in the Review of scientific advances, is being hailed as a major new step in extracting useful work from quantum computers – a step that should move the performance of quantum computing toward the much sought-after moment of quantum supremacy.
Quantum computing systems are notoriously difficult to maintain in coherent states. The fragile nature of “ordered chaos” is such that qubit information and qubit connection (entanglement) typically decay at scales well below a second. The new research brings the coherence of quantum computing to human-perceivable time scales. Using a technique they called “one-shot reading,” the researchers used precise laser pulses to add single electrons to qubits.
“[The] the light emitted reflects the absence or presence of the electron, and with almost 10,000 times more signal”, said University of Chicago graduate student Elena Glen. “By converting our fragile quantum state into stable electronic charges, we can measure our state much, much more easily. With this signal amplification, we can get a reliable answer every time we check what state the qubit is in. This type of measurement is called “single reading”, and with it we can unlock many useful quantum technologies.”
Adding single electrons is like hitting the reset button on your PC, but for quantum states. It eliminates all previously charged errors (qubits are sensitive to any external interference), allowing coherent states to “perpetuate”. The idea is to bridge the quantum and electronic domains, and the choice of material is paramount: the researchers took advantage of the inherent capabilities of silicon carbide, which can work in both domains.
“We basically created a translator to go from quantum states to the realm of electrons, which is the language of classical electronics, like what’s in your smartphone,” said Chris Anderson of the University of Chicago, the paper’s co-first author. “We want to create a new generation of devices that are sensitive to single electrons, but also host quantum states. Silicon carbide can do both, and that’s why we think it really shines.”
Although it may not seem like much, time flows differently in computing; Going from quantum stable states on the order of fractions of a second up to five seconds increases the amount of useful computational time extracted from available qubits. What’s more, it opens up new ways to increase processing power beyond just the number of qubits – the researchers calculate they can perform around 100 million quantum operations in that five-second slice. So maybe quantum computing will be a threat to Bitcoin and current government, commercial and personal encryption systems much sooner than expected?
“It is rare to have quantum information preserved on these human timescales,” said David Awschalom, senior scientist at Argonne National Laboratory. “Five seconds is enough to send a signal of the speed of light to the moon and back. This is powerful if you plan to transmit information from a qubit to someone via light. This light will always correctly reflect the state of the qubit even after circling the Earth nearly 40 times, paving the way for the creation of a distributed quantum internet.”
This technology could be combined with photonics-based quantum computing for a scalable, light-speed distributed quantum computing network. The researchers expect their results to enable the development of quantum repeaters. It is also hoped that through the use of silicon carbide, there will be opportunities for CMOS (complementary to metallic symmetry semiconductor) manufacturing technologies to integrate electronic spin-based systems into sensitive conventional electrical devices. single charges.