A game changer New Hardware Approach Revolutionizes Quantum Computing Paradigm
A potentially game-changing theoretical approach to quantum computing hardware avoids many of the complications present in current quantum computers.
On August 15, Los Alamos National Laboratory reported a strategy that could implement an algorithm in natural quantum interactions to handle a wide range of real-world problems at a much faster rate than a classical computer or a traditional gated quantum computer.
"Topologically protected Grover's oracle for the partition problem."
Quantum computing is still an emerging field because it is difficult to connect quantum bits in long strings of logic gates and to maintain the quantum entanglement required for computation. When entangled quantum bits begin to interact with the world outside the computer's quantum system and introduce errors, the entanglement collapses in a process called decoherence. This happens quickly, limiting computation time - quantum hardware has yet to achieve true error correction.
Nikolai Sinitsyn (right)
Our discovery removes many of the challenging requirements of quantum hardware," said Nikolai Sinitsyn, a theoretical physicist at Los Alamos National Laboratory. He is a co-author of this paper on the method in the journal Physical Review A. Natural systems, such as defective electron spins in diamond, have exactly the type of interactions needed for our computational process."
Sinitsyn said the research team hopes to collaborate with experimental physicists at Los Alamos to demonstrate their method using ultracold atoms. Modern ultracold atom technology is advanced enough to demonstrate such computations with about 40 to 60 quantum bits, which is enough to solve many problems that are currently unsolvable by classical or binary computation.
Instead of building a complex system of logic gates between the many quantum bits that must share quantum entanglement, the new strategy utilizes a simple magnetic field to rotate quantum bits in a natural system, such as electron spin. The precise evolution of the spin state is all that is needed to implement the algorithm.Sinitsyn says that this approach can be used to solve many of the practical problems posed by quantum computers.
The new method relies on natural entanglement rather than induced entanglement, so it requires fewer inter-quantum bit connections: this reduces the effects of decoherence. As a result, quantum bits have a relatively long lifetime.
Quantum computers can compute much faster than any classical device, but so far they have been extremely difficult to implement. Traditional quantum computers implement quantum circuits - sequences of different pairs of quantum bits to perform basic operations.
The theorists at Los Alamos have come up with an interesting alternative.
Sinitsyn says, "We note that for many well-known computational problems it is sufficient to have a quantum system with fundamental interactions in which only one quantum spin (which can be realized with two quantum bits) interacts with the other computational quantum bits. A single magnetic pulse acting only on the central spin then realizes the most complex part of the quantum Grover algorithm. This quantum manipulation is called 'Grover's oracle' and points to the desired solution."
"In this process, there is no need for direct interactions between the computational quantum bits, and no time-varying interactions with the center spin. Once the static coupling between the center spin and the quantum bits is set, the entire computational process requires only the application of simple time-varying external field pulses to rotate the spins."
The number partition problem (NPP) is one of the NP-hard (nondeterministic polynomial time completion) computational problems. The experimental team describes a rapid solution to this problem quasi-adiabatic quantum annealing steps. The figure above shows the direction of the path of the adiabatic changing magnetic field.
Top: annealing schedule; bottom: simulated annealing as a function of total time.
Importantly, the team demonstrated that this operation can be done quickly; the team also found that their method is topologically protected. That is, even without quantum error correction, it is resistant to many errors in the accuracy of the control field and other physical parameters.
Reference link:
[1] https://www.miragenews.com/revolutionary-hardware-unveils-new-quantum-1065915/
[2]https://insidehpc.com/2023/08/los-alamos-reports-hardware-approach-offers-new-quantum-computing-paradigm/
[3]https://www.eurekalert.org/news-releases/998627
[4]https://discover.lanl.gov/news/0815-quantum-computing-paradigm/
[5]https://journals.aps.org/pra/abstract/10.1103/PhysRevA.108.022412
