A Harvard-led team, supported by MIT, QuEra Computing, Caltech, and Princeton, has made a breakthrough in quantum computing, funded by DARPA. The team developed the first-ever quantum circuit with logical quantum bits (qubits), which could speed up fault-tolerant quantum computing. The researchers used arrays of “noisy” physical Rydberg qubits to create error-correcting logical qubits, a crucial step towards realizing fault-tolerant quantum computing. The team has built quantum circuits with around 48 Rydberg logical qubits, the largest number to date. The homogeneity of Rydberg qubits allows them to scale rapidly and be manipulated easily, opening up new possibilities for designing quantum computing processors.
Quantum Computing Breakthrough: DARPA-Funded Research Achieves First-Ever Quantum Circuit with Logical Qubits
A team of researchers working on the Defense Advanced Research Projects Agency’s (DARPA) Optimization with Noisy Intermediate-Scale Quantum Devices (ONISQ) program has achieved a significant breakthrough in quantum computing. The team has successfully created the first-ever quantum circuit with logical quantum bits (qubits). This discovery could potentially accelerate the development of fault-tolerant quantum computing and revolutionize the design of quantum computer processors.
The ONISQ program, which began in 2020, aimed to demonstrate the quantitative advantage of quantum information processing over classical-only supercomputers. The program pursued a hybrid concept, combining intermediate-sized “noisy” quantum processors with classical systems to solve complex optimization problems relevant to defense and commercial industries. Various teams were selected to explore different types of physical, non-logical qubits, including superconducting qubits, ion qubits, and Rydberg atomic qubits.
Harvard-led Team’s Major Breakthrough with Rydberg Qubits
The research team, led by Harvard and supported by MIT, QuEra Computing, Caltech, and Princeton, focused on exploring the potential of Rydberg qubits. They made a significant breakthrough in their research by developing techniques to create error-correcting logical qubits using arrays of “noisy” physical Rydberg qubits. Logical qubits are error-corrected to maintain their quantum state and are a critical missing piece in the puzzle to realize fault-tolerant quantum computing.
The Harvard team has built quantum circuits with around 48 Rydberg logical qubits in their laboratory, the largest number of logical qubits in existence. The team anticipates that scaling the number of logical qubits will be relatively straightforward due to the nature of Rydberg qubits and how they can be manipulated.
The Unique Characteristics of Rydberg Qubits
Rydberg qubits have the beneficial characteristic of being homogeneous in their properties, meaning each qubit behaves identically to 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 qubits allows them to scale rapidly and be manipulated and moved around easily using lasers on a quantum circuit.
The Impact of the Breakthrough on Quantum Computing
The breakthrough with Rydberg logical qubits casts new light on the traditional view that millions of physical qubits are needed before a fault-tolerant quantum computer can be developed. Given the prospect of dynamically reconfigurable quantum circuits, it’s too early to say how many logical qubits are needed to solve a particular problem. Still, it potentially could be far fewer than originally thought.
DARPA’s Role in Advancing Quantum Research
DARPA’s various quantum programs dating back to the early 2000s have aimed to build bridges between the quantum sensing and quantum information science research communities. DARPA has helped bring these communities together to advance understanding of how to control and manipulate quantum states at extremely high levels of precision.
The ONISQ research teams could build upon a rich toolbox of quantum knowledge developed across multiple DARPA quantum sensing and quantum information science programs over the past several years. This merging of research fields helped facilitate the discovery that Rydberg atoms can be used to create error-corrected, logical qubits.
“Rydberg qubits have the beneficial characteristic of being homogenous in their properties – meaning each qubit is indistinguishable from the next in how they behave,” said Dr. Mukund Vengalattore, ONISQ program manager in DARPA’s Defense Sciences Office. “That’s not the case for other platforms such as superconducting qubits where each qubit is unique and therefore not interchangeable. The homogeneity of Rydberg qubits allows them to scale rapidly and also allows them to be manipulated and moved around easily using lasers on a quantum circuit. This overcomes the current error-prone methods of performing qubit operations by having to connect them sequentially, which propagates errors throughout the chip. It’s now possible to imagine dynamic reconfiguration of qubits on a quantum chip, where you’re no longer limited to a sequential process of running quantum circuits. Now, you can bring entire collections of qubits, all of them, from one place in the circuit to another place on the circuit using laser tweezers, run an operation, and then put them back where they were originally. Dynamically reconfigurable and transportable Rydberg logical qubits open up completely new concepts and paradigms for designing and building scalable quantum computing processors.”
“If anyone had predicted three years ago when the ONISQ program began that Rydberg neutral atoms could function as logical qubits, no one would have believed it,” said Dr. Guido Zuccarello, a DARPA technical adviser who has supported the ONISQ program since its start in 2020. “It’s the DARPA way to bet on the potential of these less-studied qubits along with the more well-studied ions and superconducting circuits. As an exploratory program, ONISQ gave researchers the leeway to explore unique and new applications beyond just the optimization focus. As a result, the Harvard-led team was able to leverage much more of the potential of these Rydberg qubits and turn them into logical qubits, which is a very significant discovery.”
“This merging of research fields building on results from a series of preceding DARPA-led quantum efforts helped facilitate the discovery that Rydberg atoms can be used to create error-corrected, logical qubits,” Vengalattore said. “As exciting and transformative as these results are, we see this as a stepping stone towards a longer-term vision of actualizing disruptive pathways to error-corrected quantum computing and other areas of quantum technology.”
Summary
A team of researchers, funded by DARPA and led by Harvard, has made a significant breakthrough in quantum computing by creating the first-ever quantum circuit with logical quantum bits (qubits), which could speed up the development of fault-tolerant quantum computing. The team developed techniques to create error-correcting logical qubits using arrays of “noisy” physical Rydberg qubits, a critical step towards solving complex problems and potentially reducing the number of qubits needed for a fault-tolerant quantum computer.
- A team of researchers funded by DARPA (Defense Advanced Research Projects Agency) has made a significant breakthrough in quantum computing.
- The team, led by Harvard and supported by MIT, QuEra Computing, Caltech, and Princeton, has created the first-ever quantum circuit with logical quantum bits (qubits). This key development could speed up fault-tolerant quantum computing.
- The research was part of DARPA’s Optimization with Noisy Intermediate-Scale Quantum devices (ONISQ) program, which began in 2020 — the program aimed to demonstrate the advantages of quantum information processing over classical supercomputers.
- The team focused on the potential of Rydberg qubits, developing techniques to create error-correcting logical qubits using arrays of “noisy” physical Rydberg qubits. Logical qubits are error-corrected to maintain their quantum state, making them helpful in solving complex problems.
- Harvard has built quantum circuits with around 48 Rydberg logical qubits, the largest number of logical qubits. The nature of Rydberg qubits allows for rapid scaling and easy manipulation.
- Dr. Mukund Vengalattore, ONISQ program manager in DARPA’s Defense Sciences Office, highlighted the homogeneity of Rydberg qubits as a critical advantage, allowing for dynamic reconfiguration of qubits on a quantum chip.
- The breakthrough challenges the traditional view that millions of physical qubits are needed for a fault-tolerant quantum computer, suggesting that fewer logical qubits may be required.