NIST’s quantum artithmetic-logic unit demonstrated sustained operations that proved the feasibility of large-scale quantum computers. The quantum computer maintained a 94 percent accuracy rate in multistep operations for quantum bits. These qubits passed intermediate results to the next processing stage for up to 15 seconds. NIST’s 94 percent accuracy rate will have to be raised to 99.9 percent to make quantum computing commercially feasible.
Large-scale quantum information processors must be able to transport and maintain quantum information, and repeatedly perform logical operations. Here, we demonstrate a combination of all the fundamental elements required to perform scalable quantum computing using qubits stored in the internal states of trapped atomic ions. We quantify the repeatability of a multi-qubit operation, observing no loss of performance despite qubit transport over macroscopic distances. Key to these results is the use of different pairs of 9Be+ hyperfine states for robust qubit storage, readout and gates, and simultaneous trapping of 24Mg+ “re-cooling” ions along with the qubit ions.
4 page pdf with supplemental information. The work was done with two qubits but prove that large scale trapped ion quantum computer can work.
The sequence of quantum operations used five arithmetic-logic operations–four single-qubit operations and a two-qubit operation–involving 10 transport operations. The sequence of operations took about 20 milliseconds and was repeated 3,150 times for each of 16 different starting states. The sustained operations could be performed for as long as 15 seconds before errors occurred. The current prototype used no error-correction procedures, but was constructed to test the limits of trapped-ion quantum computers.
Trapped-ion quantum computers store qubits on electrically charged atoms–NIST used beryllium ions–which were isolated inside a dark slit between the gold-covered alumina wafers measuring just 3.5 millimeters long and 200 microns wide. The trapped beryllium ions were moved among six zones in the trap. Operations were preformed using lasers to initialize the ions in a known quantum state, store data as operands, perform several one- and two-qubit operations during which intermediate results were transported between traps and then read out the final result.
“Next, we want to improve our accuracy, which involves building better, more powerful lasers,” said Homes, “as well as demonstrate operations using more qubits in more complicated computing tasks