A theoretical approach to quantum computing hardware that could alter the game does away with much of the troublesome complexity of existing quantum computers. The method uses a natural quantum algorithm to process a range of practical issues more quickly than either classical computers or traditional gate-based quantum computers can.
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Our finding eliminates many challenging requirements for quantum hardware. Natural systems, such as the electronic spins of defects in diamond, have precisely the type of interactions needed for our computation process.
Nikolai Sinitsyn, Study Co-Author and Theoretical Physicist, Los Alamos National Laboratory
To test their method utilizing ultracold atoms, Sinitsyn said the team plans to work with experimental physicists at Los Alamos. According to him, existing ultracold atom technologies are sufficiently developed to show such calculations with between 40 and 60 qubits, which is adequate to tackle a wide range of issues that are not currently amenable to conventional, or binary, computation. Similar to a bit in well-known conventional computers, a qubit is the fundamental building block of quantum information.
Longer-Lived Qubits
The new method rotates the qubits, such as the spins of electrons, in a natural system rather than constructing a complicated system of logic gates among several qubits that must all share quantum entanglement. All tequired to put the method into practice is a precise development of the spin states. According to Sinitsyn, the strategy could be utilized to address a variety of real-world issues raised by quantum computing.
The challenge of sustaining the necessary quantum entanglement for processing while connecting qubits in lengthy chains of logic gates hinders quantum computing, which is still an emerging field of science.
As the entangled qubits start to interact with the environment outside the computer’s quantum system, causing mistakes, entanglement dissipates in a process known as decoherence. The computation time is short since that occurs rapidly. On-chip quantum technology has not yet been used for true error correction.
The new method requires fewer connections between qubits since it depends on natural rather than induced entanglement. Decoherence’s effects are lessened as a result. Thus, according to Sinitsyn, the qubits have a long lifespan.
The theoretical study published by the Los Alamos researchers demonstrated how the technique might solve a number-partitioning issue using Grover’s algorithm quicker than existing quantum computers. It is one of the most well-known quantum algorithms, and it enables unstructured searches of large information sets, which consume traditional computer resources.
Grover’s approach, for example, Sinitsyn explained, can be used to divide up the runtime for tasks evenly across two computers so that they finish at the same time, in addition to other useful activities. Although it is ideally suited to idealistic, error-corrected quantum computers, the procedure is challenging to implement on today's error-prone machines.
Protected Against Errors
Quantum computers are designed to execute computations considerably faster than any classical device, but they have been incredibly difficult to implement so far, according to Sinitsyn. A traditional quantum computer employs quantum circuits, which are sequences of basic operations performed on distinct pairings of qubits.
Theorists at Los Alamos presented an intriguing option.
Sinitsyn added, “We noticed that for many famous computational problems it is sufficient to have a quantum system with elementary interactions, in which only a single quantum spin—. realizable with two qubits—interacts with the rest of the computational qubits. Then a single magnetic pulse that acts only on the central spin implements the most complex part of the quantum Grover’s algorithm.”
This quantum operation, known as Grover’s oracle, points to the required answer.
No direct interactions between the computational qubits and no time-dependent interactions with the central spin are needed in the process.
Nikolai Sinitsyn, Study Co-Author and Theoretical Physicist, Los Alamos National Laboratory
Once the static couplings between the central spin and the qubits are established, the entire computation consists of applying simple time-dependent external field pulses to rotate the spins, he explained.
Importantly, the team demonstrated that such operations can be completed quickly. The researchers also discovered that their method is topologically secure. That is, even without quantum error correction, it is resistant to numerous faults in the accuracy of the control fields and other physical characteristics.
Los Alamos National Laboratory’s Laboratory Directed Research and Development program, the Department of Energy Office of Science, and the Office of Advanced Scientific Computing Research provided funding for the study.
Journal Reference:
Sinitsyn, N. A., et al. (2023) Topologically protected Grover's oracle for the partition problem. Physical Review A. doi:10.1103/PhysRevA.108.022412