Atom computing system. The rows of atoms are spaced far enough apart that a single laser (green bar) sent across them affects only individual atoms. Once the atoms move into the interaction zone (red bar), the laser can gate the pair of atoms. Spaces that can hold atoms can be left empty to avoid performing unnecessary operations.
Credit: Reichardt et al.
The machine used in the new demonstration will host 256 of these neutral atoms. Atom Computing arranges atoms in a series of parallel rows with spaces between them so that they can be shuffled. For a single-qubit gate, you can shine a laser across the row and force every atom the laser touches to perform its operation. For a two-qubit gate, a pair of atoms is moved to the end of the row, moved a certain distance apart, and the laser gates all pairs present at that point.
Atom’s hardware also allows for a continuous supply of new atoms to replace lost atoms. It is also possible to image the atomic arrangement between operations to determine whether any atoms are missing or in the wrong state.
it’s just logical
In general, the more hardware qubits you allocate to each logical qubit, the more simultaneous errors you can identify. This identification allows two ways to handle errors. The first method simply discards the calculation that caused the error and starts over. The second method allows you to use information about the error to attempt a repair, but the repair involves additional operations that may cause other errors.
In this work, the Microsoft/Atom team used relatively small logical qubits (that is, they used very few hardware qubits). This means that the machine can fit more logical qubits within the total 256 hardware qubits available. We also checked the error rates for both error detection by discard and error detection by correction.
The research team conducted two main demonstrations. One was to put 24 of these logic qubits into a so-called cat state, named after Schrödinger’s hypothetical feline. This is the case when the probability of a quantum object being in two mutually exclusive states at the same time is non-zero. In this case, the researchers placed 24 logical qubits in an entangled cat state. This is the largest ensemble of its kind ever created. Apart from that, they implemented something called Bernstein-Vazirani algorithm. The classic version of this algorithm requires a separate query to identify each bit in the string. The quantum version retrieves the entire string in a single query, making it a notable case where quantum acceleration is possible.
