Recently, the California Institute of Technology's Manuel M. The lab of Prof. Manuel A. Endres has released the world's largest quantum computing platform to date.
The researchers demonstrated that 6,100 neutral atoms were captured with an array of 12,000 optical tweezers, achieving a decoherence time of 12.6 seconds and a vacuum lifetime of 23 minutes.
The results were released and immediately sent shockwaves through academia and industry. Some well-known academics have called the research "the greatest work" in the field, while the industry believes that the research "will have the potential to dismantle the cryptographic mechanism of Bitcoin".
The study indicates that quantum computing may be realized in the short term, and it is expected to be applied in the foreseeable future.
(Source: California Institute of Technology)
What would it mean if we could use quantum computing to explore, simulate, and understand the world?
This shows that the way human beings perceive the world has undergone a fundamental change, and we will enter a new era of explosive computing power.
Prior to this, human cognition of the world had certain limitations. One reason for this is that the whole world is a complex system. From microscopic molecules and atoms to macroscopic weather systems, they are far more complex than existing computers can calculate.
The emergence of quantum computing is expected to solve the problems that could not be broken through due to the complexity of computing and insufficient computing power, and bring revolutionary changes to human society and the development of science and technology, including artificial intelligence, superconductivity, biomedicine, new materials, encryption and decryption and many other fields.
For example, research on disease mechanisms, including molecular interactions between proteins, and drug discovery may lead to faster breakthroughs.
On the other hand, people can also use the computing power far beyond all the current chips to build unprecedented artificial intelligence models and accelerate the pace of realizing general-purpose artificial intelligence.
Recently, a related paper was published on the preprint website arXiv under the title "A tweezer array with 6100 highly coherent atomic qubits" [1]. It is reported that the paper is currently in the status of review of the international top journal.
California Institute of Technology master's student Hannah M. Hannah J. Manetsch, Gyohei Nomura, and Elie Bataille are co-first authors. Professor Manuel A. Endres co-led the study.
Figure丨Related papers (source: arXiv)
The current state of quantum computing: It is still in the stage of analog computing
Quantum computing has been a dream for a long time, first proposed by Richard Feynman, a member of the National Academy of Sciences and a Nobel laureate in physics.
It is a completely new way of information processing, based on the principles of quantum mechanics, which is very different from the traditional way of computing based on the laws of classical physics.
Specifically, in classical computing, information is encoded in bits, each bit either 0 or 1. In quantum computing, the basic unit of information is the qubit, which can be in a state of 0 and 1 at the same time, and this state is called "quantum superposition".
Quantum superposition gives quantum computers the potential to process large amounts of data, theoretically achieving exponentially faster computing speeds than classical computers. Another key property of qubits is quantum entanglement. When two qubits are entangled, the state of one qubit instantly affects the state of the other.
At the same time, we must also note that although people's expectations for quantum computing are high, quantum computing has not yet achieved substantial practical applications.
The main reason for this is that quantum computing requires complex, large-scale quantum systems, and some existing quantum computing can achieve a very limited number of high-quality bits on hardware.
In addition, the necessary conditions for the realization of quantum computing are high precision and high accuracy, and it cannot be ignored that qubits are highly susceptible to noise and interference in actual operation.
So, in fact, we have been in the stage of analog computing, and we have not really entered the era of digital computing.
A quantum processor with the highest number of qubits to date
It is important to understand that many physical bits can be combined into a single logical bit. The accepted practice of realizing quantum computing in the industry is to make the quantum system larger, and then use Quantum Error Correction (QEC) to reduce the error rate of quantum computing.
Previous quantum processors were capable of achieving tens to hundreds of qubits at most. Recently, there have been reports in the field that quantum systems achieve about 1000 atoms, but do not define qubits or exhibit coherent control.
"We've achieved an order of magnitude increase in the number of qubits compared to previous studies, which I think is a landmark progress. Lv Xudong said.
The reason why this research has been able to develop a quantum processor with the largest number of qubits so far and achieve satisfactory results in all aspects is inseparable from the technical path of the researchers' selection of neutral atoms.
In 1947, American physicist William Shockley invented the transistor to replace the vacuum tube in computer design. However, these small parts require semiconductor materials to work.
In classical computing, when the concept of a semiconductor was first proposed, it was not clear which material would be used to make it. Early transistors contained germanium, and after trial and comparison, silicon was finally chosen to make semiconductors precisely because it could be scaled and integrated.
Similarly, the neutral atom is a qubit implementation method, and the key steps such as atom preparation, quantum-controlled gate operation, quantum state measurement, error correction, and quantum storage can be continuously improved and greatly scalable.
The team put an atom in each optical tweezer and captured 6,100 qubits with 12,000 optical tweezers.
(Source: arXiv)
It is understood that the construction of the entire system took nearly three years. The team combined optical tweezers with polarization and focused through a high numerical aperture objective with a field of view diameter of 1.5mm, providing a wide field for qubit capture and manipulation in ultra-high vacuum.
In order to minimize the factors that interfere with the atoms, reduce the heating effect of the optical tweezers, and make it evenly distributed in the optical tweezers, the researchers designed a special far-resonance wavelength in a room-temperature vacuum chamber to achieve low-loss, high-fidelity imaging, and long-ultra-fine coherence time imaging.
The system was fraught with challenges during preparation. For example, after a large number of atoms have been generated, it is necessary to ensure that they are evenly distributed in the optical tweezers, which requires a light intensity of about 100-200W. In this regard, the paper describes that such a strong laser is rare in cold atom experiments, and the problems such as the temperature increase of optical components need to be solved.
In addition, if the lifetime of an atom is very short, the more atoms in the whole system, the higher the probability of it making mistakes, so it is necessary to increase the lifetime of the atom as much as possible.
Figure丨Schematic diagram of the experimental system (source: arXiv)
In order to solve this problem, the researchers used a series of methods such as atomic cooling and atomic trapping to cool the atoms with a 2D polarization gradient of about 10 milliseconds. At the same time, the experimenters used an extremely high vacuum to create a very clean background environment, which greatly avoided the influence of background particles on the experimental atoms.
With this method, the vacuum lifetime of the atoms in the optical tweezers of nearly 23 minutes was also achieved, which is currently the longest vacuum lifetime of the atoms in the optical tweezers without the use of a cryogenic system. "We've kept the entire important process in the millisecond order, so the 20-odd minutes are almost error-free. Lv Xudong said.
The coherence time is closely related to maintaining quantum properties, and the researchers also achieved a decoherence time of 12.6 seconds. This is the longest decoherence time of an alkali metal atom in optical tweezers to date, which is about an order of magnitude improvement compared to previous studies.
At the same time, they also showed the imaging of a single cesium atom and set a new record. Among them, the imaging survival probability is 99.98952%, and the imaging fidelity is 99.99374%.
"Our results, together with the rearrangement and specific error correction codes, if a high-fidelity quantum computer with about 10,000 atomic qubits are a possible prospect in the near future, provides a new path to quantum error correction with hundreds of logical qubits. Lu Xudong said.
It is expected to usher in a new era of quantum computing
Xudong graduated from the School of Physics of Peking University and the University of California, Berkeley with a bachelor's degree and a Ph.D. degree, respectively, and his main research direction was quantum precision measurement and instrumentation.
During his Ph.D., he studied under Alexander Pines, Fellow of the National Academy of Sciences and American Academy of Arts and Sciences, and Professor Jeffrey Reimer, Dean of the School of Chemical and Biomolecular Engineering at the University of California, Berkeley.
Figure丨Lv Xudong (second from right in the first row) and his research group (source: Lv Xudong)
Currently, Xudong Lu is engaged in postdoctoral research at the California Institute of Technology. Prof. Manuel A. Endres.
Since 2016, the research group has used neutral atoms to perform quantum computing and quantum simulation, and realized the capture of atoms with optical tweezers, and the rearrangement of atoms to achieve optical tweezer arrays through this method. Recently, they have also developed a new method to predict the error rate of quantum computers without being fully simulated by classical computers [2].
"It is the team's solid technical accumulation over the years that has led to this new achievement. Lu Xudong said.
In fact, it is easy to move atoms in optical tweezers, because the atomic system is more flexible and any two bits can interact with each other.
Based on this advantage, another research group achieved 48 logical bits on a neutral quantum computing platform earlier this year [3].
It is understood that no other platform has ever achieved such efficient logical bits, which is also an exciting development that demonstrates the advantages of a neutral atomic path. "The quality of the logical bits of neutral atomic systems will also get higher and higher in the future," he said. ”
According to the paper, the next step is to continue to increase the number of bits on the one hand, and on the other hand, the position of the 6,100 qubits in the experiment is random, and the researchers intend to arrange them in an orderly manner. In addition, they will also explore directions such as quantum error correction in quantum gate circuits.
Lv Xudong believes that quantum computing may be implemented earlier in quantum simulation or simulated material system observation of new states of matter, and will also play a huge role in artificial intelligence. "I'm optimistic about quantum computing and I believe it won't be long before it's first available. ”
The milestone significance of this research is that it demonstrates the scalability of quantum processor systems, and to a certain extent, it opens up the era of large-scale bit quantum computing. On this basis, quantum computing is expected to open a new era. By analogy with traditional computers, this may be the beginning of the transition from the "era of vacuum tubes" to the "era of integrated circuits".
Resources:
1.Manetsch, Hannah J., et al. A tweezer array with 6100 highly coherent atomic qubits. arXiv:2403.12021(2024). https://arxiv.org/abs/2403.12021
2.Shaw, A.L., Chen, Z., Choi, J. et al. Benchmarking highly entangled states on a 60-atom analogue quantum simulator. Nature 628, 71–77 (2024). https://doi.org/10.1038/s41586-024-07173-x
3.Bluvstein, D., Evered, S.J., Geim, A.A. et al. Logical quantum processor based on reconfigurable atom arrays. Nature 626, 58–65 (2024). https://doi.org/10.1038/s41586-023-06927-3
Typesetting: Liu Yakun