This extreme vulnerability may make quantum computing sound hopeless. However, in 1995, applied mathematician Peter Scholl discovered A smart way to store quantum information. His encoding had two important characteristics. First, it can tolerate errors that only affect individual qubits. Second, it has built-in procedures to correct errors as they occur, preventing them from accumulating and disrupting calculations. Scholl’s discovery was the first example of a quantum error-correcting code, and his two key properties have become hallmarks of all such codes.
The first characteristic arises from a simple principle. In other words, secret information becomes less vulnerable when divided. Spy networks employ similar strategies. Each spy knows almost nothing about the network as a whole, so even if an individual is captured, the organization remains safe. However, quantum error correcting codes take this logic to the extreme. In a quantum spy network, no single spy knows anything at all, but together they can know a lot.
Each quantum error correcting code is a specific recipe for distributing quantum information across many qubits in a collective superposition state. This step effectively converts a cluster of physical qubits into a single virtual qubit. Repeating this process many times on a large array of qubits yields a large number of virtual qubits that can be used to perform calculations.
The physical qubits that make up each virtual qubit are like unknowing quantum spies. Measuring any of them tells us nothing about the state of the virtual qubit to which it belongs, a property called local indistinguishability. Each physical qubit encodes no information, so errors in a single qubit cannot ruin the calculation. Important information is somehow everywhere, but not in a specific location.
“You can’t pin it down to individual qubits,” Cubitt says.
All quantum error correcting codes can absorb at least one error without affecting the encoded information, but eventually all of them disappear as the errors accumulate. This is where the second property of quantum error correcting codes comes into play: actual error correction. This is closely related to local indiscernibility. Since errors in individual qubits do not destroy information, it is always possible to: undo error Use established procedures specific to each code.
I was taken for a drive.
ShiliA postdoctoral fellow at the Perimeter Institute for Theoretical Physics in Waterloo, Canada, he was familiar with the theory of quantum error correction.But when he struck up a conversation with his colleague, the topic was far from his mind. Latham Boyle. It was the fall of 2022, and the two physicists were on an evening shuttle from Waterloo to Toronto. Mr. Boyle, an expert on aperiodic tiles who was then living in Toronto and now at the University of Edinburgh, was a familiar face on the shuttle buses that often got stuck in traffic.
“Under normal circumstances, they could be in a very dire situation,” Boyle said. “This was like the best thing ever.”
Before that fateful night, Lee and Boyle were aware of each other’s research, but their fields of research did not directly overlap and they had never had one-on-one conversations. But like countless researchers in unrelated fields, Lee was interested in aperiodic tiling. “It’s very hard not to be interested,” he said.