Scientists use neutral atoms to prepare quantum processors, achieving 6,100 quan

Recently,the laboratory of Professor Manuel A.Endres at the California Institute of Technology released the world's largest quantum computing platform to date.

Researchers demonstrated the capture of 6,100 neutral atoms using an array of 12,000 optical tweezers,achieving a decoherence time of 12.6 seconds,and reaching a vacuum lifetime of 23 minutes.

The release of this result immediately caused a stir in the academic and industrial communities.Some well-known scholars have called this research the "greatest work" in the field,while the industry believes that this research "may have the potential to undermine the encryption mechanism of Bitcoin."

This research heralds the possibility of quantum computing being realized in the short term and is expected to be applied in the foreseeable future.

What does it mean if we can explore,simulate,and understand the world through quantum computing?This indicates that the way humans perceive the world has undergone an essential change,and we are about to enter a new era of computational power explosion.

Before this,human cognition of the world had certain limitations.One of the reasons is that the entire world is a complex system.From microscopic molecules and atoms to macroscopic weather systems,the degree of complexity far exceeds the level that existing computers can calculate and simulate.

The emergence of quantum computing is expected to solve problems that were previously unable to be broken through due to computational complexity and insufficient computing power,bringing revolutionary changes to human society and technological development,including artificial intelligence,superconductivity,biomedicine,new materials,encryption and decryption,and many other fields.

For example,research on the mechanisms of diseases such as molecular interactions between proteins,and drug development,may achieve breakthroughs more quickly based on this.

On the other hand,people can also use computational power that far exceeds all current chips to build unprecedented large artificial intelligence models,accelerating the pace of achieving general artificial intelligence.Recently,a related paper titled "A tweezer array with 6100 highly coherent atomic qubits" was published on the preprint website arXiv[1].It is reported that the paper is currently under review for an international top journal.

Hannah J.Manetsch,Gyohei Nomura,and Elie Bataille,graduate students at the California Institute of Technology,are the co-first authors of the paper.Dr.Xudong Lu,a postdoctoral researcher at the same institution,and Professor Manuel A.Endres are responsible for the research together.

Current status of quantum computing: Still in the stage of simulation computing

Quantum computing has been a long-standing dream,first proposed by Richard Feynman,a member of the National Academy of Sciences in the United States and a Nobel laureate in physics.It is an entirely new way of processing information,based on the principles of quantum mechanics,which is completely different from the traditional computation methods based on the laws of classical physics.

Specifically,in classical computing,information is encoded in bits,with each bit being either 0 or 1.In contrast,in quantum computing,the fundamental unit of information is the quantum bit,or qubit,which can exist simultaneously in states of both 0 and 1.This state is known as "quantum superposition."

Quantum superposition endows quantum computers with the potential to process vast amounts of data,and theoretically,it can achieve computational speeds that are exponentially faster than those of traditional computers.Another key characteristic of qubits is quantum entanglement.When two qubits are entangled,the state of one qubit can instantaneously affect the state of the other.

At the same time,we must also recognize that,although there are high expectations for quantum computing,it has not yet achieved substantial practical applications.

The main reason is that quantum computing requires complex,large-scale quantum systems,and the number of high-quality bits that can be realized in hardware by some existing quantum computers is very limited.In addition,the necessary conditions for the implementation of quantum computing are high precision and high accuracy.It cannot be ignored that quantum bits are extremely susceptible to noise and interference in actual operations.

Therefore,in reality,we have always been in the stage of analog computing and have not truly entered the era of digital computing.

The quantum processor with the highest number of quantum bits to date

It should be understood that many physical bits are needed to combine into a logical bit.The widely recognized approach to achieving quantum computing in the industry is to make the quantum system larger,and then use quantum error correction (Quantum Error Correction,QEC) to reduce the error rate of quantum computing.Previous quantum processors have been able to achieve only tens to hundreds of quantum bits.Recently,there have been reports in the field that a quantum system has achieved about 1000 atoms,but it has not defined quantum bits or demonstrated coherent control.

"We have increased the number of quantum bits by about an order of magnitude compared to previous research,and I believe this is a milestone-level progress," said Lu Xudong.

The reason why this research has been able to develop the quantum processor with the highest number of quantum bits to date and achieve relatively ideal results in all aspects is closely related to the researchers' choice of the technical path of neutral atoms.

In 1947,American physicist William Shockley invented the transistor,which replaced the vacuum tube in computer design.However,these small components need semiconductor materials to work.

In classical computing,after the concept of semiconductors was first proposed,it was not certain which specific material to use to make it.Early transistors contained germanium,and after trials and comparisons,silicon was ultimately chosen for preparing semiconductors,precisely because it can be scaled and integrated.Similar to this,neutral atoms are a method of implementing quantum bits,including key steps such as atomic preparation,quantum controlled gate operations,quantum state measurement,error correction,and quantum storage,all of which can be continuously improved and developed,and have great scalability.

The team placed one atom in each optical tweezer,capturing 6100 quantum bits with 12000 optical tweezers.

It is understood that the entire system took nearly three years to build.The team combined optical tweezers with polarization,focusing through a high numerical aperture objective lens with a field of view diameter of 1.5mm,providing a vast area for the capture and operation of quantum bits in ultra-high vacuum.

To minimize factors that interfere with the atoms,reduce the heating effect of the optical tweezers,and evenly distribute them,researchers designed a special far-resonant wavelength in a room temperature vacuum chamber,thus achieving low loss,high fidelity imaging,and long super fine coherence time imaging.

The system was full of challenges during the preparation process.For example,after generating a large number of atoms,it is necessary to ensure that they are evenly distributed in the optical tweezers,which requires the light intensity to reach about 100-200W.In this regard,the paper describes: such a strong laser is not common in cold atom experiments,and the problems caused by the increase in temperature of optical components need to be solved.Additionally,if the lifetime of an atom is very short,the more atoms in the entire system,the higher the probability of errors,so it is also necessary to extend the lifetime of the atoms as much as possible.

To address the aforementioned issue,researchers have employed a series of methods such as atomic cooling and atomic capture to cool the atoms for about 10 milliseconds with a 2D polarization gradient.At the same time,the experimenters used an extremely high vacuum to create a very clean background environment,greatly avoiding the impact of background particles on the experimental atoms.

Through this method,the experiment also achieved a vacuum lifetime of nearly 23 minutes for the atom in the optical tweezers,which is the longest vacuum lifetime of the atom in the optical tweezers without using a low-temperature system at present."We control the entire important process at the millisecond level,so this more than 20 minutes of time can be almost error-free," said Lv Xudong.

Coherence time is closely related to maintaining quantum properties,and researchers have also achieved a decoherence time of 12.6 seconds.This is the longest decoherence time of alkali metal atoms in optical tweezers to date,which is about one order of magnitude higher than previous studies.

At the same time,they also demonstrated 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,combined with reordering and specific error-correcting codes,if a high-fidelity quantum computer with approximately 10,000 atomic qubits is a near-term prospect,provide a new path for achieving quantum error correction with hundreds of logical qubits," said Lu Xudong.

The prospect of ushering in a new era of quantum computing.

Lu Xudong graduated with a bachelor's and a Ph.D.from the School of Physics at Peking University and the University of California,Berkeley,respectively.His main research direction during his Ph.D.was quantum precision measurement and instrumentation.

During his doctorate,he studied under Alexander Pines,a member of the U.S.National Academy of Sciences and the American Academy of Arts and Sciences,and Professor Jeffrey Reimer,Dean of the College of Chemistry and Biochemical Engineering at the University of California,Berkeley.Currently,Lv Xudong is engaged in postdoctoral research at the California Institute of Technology,with Professor Manuel A.Endres as his collaborating advisor.

This research group has been utilizing neutral atoms for quantum computing and quantum simulation since 2016,achieving the capture of atoms with optical tweezers and rearranging them to form an optical tweezer array through this method.Recently,they have also developed a new method that allows for the prediction of quantum computer error rates without the need for complete simulation by classical computers [2].

"It is precisely the solid technical accumulation of the team over the years that has led to this new achievement," said Lv Xudong.

In fact,placing atoms in optical tweezers can easily cause movement,as the atomic system is quite flexible,allowing any two bits to interact with each other.

Leveraging this advantage,another research group achieved 48 logical qubits on a neutral quantum computing platform earlier this year [3].It is understood that no other platform has ever achieved such highly efficient logical qubits,which is an exciting development that demonstrates the advantages of the neutral atom approach.He said: "The quality of logical qubits in neutral atom systems will also continue to improve in the future."

According to the paper,the next step,the research team plans to continue increasing the number of qubits on one hand; on the other hand,the current 6100 qubits are randomly positioned in the experiment,and researchers intend to arrange them orderly.In addition,they will also explore directions such as quantum gate circuit quantum error correction.

Lu Xudong believes that quantum computing may be more likely to be applied earlier in quantum simulation or simulating material systems to observe new states of matter,and it will also play a huge role in artificial intelligence."I have a more optimistic attitude towards quantum computing and believe that it will soon be initially usable."

The milestone significance of this research lies in demonstrating the scalability of quantum processor systems,to some extent,it has opened the era of large-scale qubit quantum computing.On this basis,quantum computing is expected to usher in a new era.Analogous to traditional computers,this may be the beginning of the transition from the "vacuum tube era" to the "integrated circuit era."