Posted in Beijing 2023-12-11 15:27
Figure: Harvard-led team develops novel logical qubits to enable scalable quantum computing.
A team of researchers working on the DARPA Noise Mesoscale Quantum Device Optimization (ONISQ) program has created the first-ever quantum circuit with logical qubits (qubits), a key discovery that could accelerate fault-tolerant quantum computing and revolutionize the concept of fault-tolerant quantum computing, according to Space.com on December 8.
Launched in 2020, the ONISQ program aims to demonstrate the quantitative advantages of quantum information processing by surpassing the performance of classical supercomputers to solve a particularly challenging problem called combinatorial optimization. The program pursues a hybrid concept that combines medium-sized "noisy" or error-prone quantum processors with classical systems specifically designed to solve optimization problems of interest to the defense and commercial industries. Select teams to explore various types of physical, non-logical qubits, including superconducting qubits, ion qubits, and Rydberg atomic qubits.
The Harvard research team, with support from MIT, Queracomputing, Caltech, and Princeton University, focused on exploring the potential of Rydberg qubits and made a major breakthrough in the research process: the team developed techniques to create error-correcting logic qubits using qubits. "Noisy" physics Rydberg qubit arrays. Logical qubits are a critical missing piece in the puzzle of implementing fault-tolerant quantum computing. In contrast to error-prone physical qubits, logical qubits undergo error correction to maintain their quantum state, allowing them to be used to solve a variety of complex problems.
To date, Harvard University has built quantum circuits containing about 48 Rydberg logic qubits in its lab, which is the largest number of logic qubits in existence. Due to the nature of the Rydberg qubits and how they are manipulated, it is expected that rapidly scaling the number of logical qubits will be relatively straightforward.
Dr. Mukundvengalattore, ONISQ Program Manager at the DARPA Defense Science Office, said: "Rydberg qubits have beneficial characteristics that are homogeneous in nature, which means that each qubit behaves in no different way than the next. This is not the case for other platforms, such as superconducting qubits, where each qubit is unique and therefore not interchangeable. "The homogeneity of Rydberg's qubits allows them to scale quickly, and also allows them to be easily manipulated and moved using lasers on quantum circuits. This overcomes the current error-prone method of performing qubit operations, which must connect them sequentially, propagating errors throughout the chip.
Now you can imagine the dynamic reconfiguration of qubits on a quantum chip, and you are no longer limited to the sequential process of running a quantum circuit. You can now use laser tweezers to take the entire collection of qubits from one location in the circuit to another, run the operation, and then put them back in their original positions. Dynamically reconfigurable and transferable Rydberg logic qubits open up entirely new concepts and paradigms for designing and building scalable quantum computing processors.
If there had been someone three years ago when the ONISQ project started that Rydberg neutral atoms could act as logical qubits, no one would have believed it," said Dr. Guido Zuccarello, a technical advisor to DARPA who has supported the ONISQ project since its inception. As an exploratory program, ONISQ gives researchers leeway to explore unique and new applications, rather than just optimizing focus. ”
While it is expected that at least an order of magnitude larger than 48 logical qubits will be needed to solve any major problem envisioned by quantum computers, the breakthrough of Rydberg logical qubits provides a new perspective to the conventional wisdom that millions of physical qubits are needed before failures can be developed into forgiving quantum computers. Given the promise of dynamically reconfigurable quantum circuits, it is too early to say how many logical qubits are needed to solve a particular problem.
Since the early 2000s, DARPA's various quantum projects have focused on building bridges between the quantum sensing and quantum information science research communities, which have traditionally been siloed. DARPA helps bring these communities together to advance understanding of how quantum states can be controlled and manipulated with extreme precision.
"The ONISQ research team can tap into the rich toolbox of quantum knowledge developed by DARPA's multiple quantum sensing and quantum information science projects over the past few years," Vengalattore said. The toolbox contains in-depth foundational and technical insights from a number of DARPA projects, including OLE [optical lattice device], Quasar [quantum-assisted sensing and readout], ATN [All Together Now], and DrinQS [driven and non-equilibrium quantum systems]. ”
Vengalattore highlighted that bringing together the quantum sensing and quantum information science community under ONISQ could apply Rydberg quantum sensing knowledge to quantum computing challenges at a speed that few would have anticipated just a few years ago.
"The merger of research areas based on a series of previous quantum research results led by DARPA has helped facilitate the discovery that Rydberg atoms can be used to create error-correcting logic qubits," Vengalattore said. While these results are exciting and transformative, we see them as a stepping stone to a long-term vision of disruptive pathways to error-correcting quantum computing and other areas of quantum technology. ”