Three Nature articles in one day! IBM's error correction upgrades, processors run at much higher temperatures, and high-energy sub-particles are seen for the first time!
On the way to exploring the potential and challenges of quantum computing, scientists have been trying to find effective ways to improve the error correction capability of quantum computers. This task, which plays a central role in quantum computers solving real-world problems, has gained broad consensus in the industry. While there is no unanimity on the best technological path to achieve this goal, a number of industry giants including Microsoft, Intel, Amazon and IBM are investing in research and development of different technologies, while a number of startups are exploring a wider range of potential solutions.
This daunting task has forced researchers to undertake a number of exciting R&D endeavors, and some of these could end up being key milestones in the evolution of quantum computing. In order to better understand these efforts, ICV will present three important research papers published in the latest issue of Nature.
These studies not only contribute to the theoretical and practical aspects of quantum computing, but also demonstrate the efforts and innovations of scientists in this challenging field.
The first paper, from the Diraq team, demonstrates their development of a quantum processor that can operate at higher temperatures. Compared to conventional quantum computers, Diraq's quantum processor is able to operate stably at temperatures up to 20 times higher while maintaining high accuracy. This technology reduces the reliance of quantum computers on complex cooling systems, helping to apply quantum computers to a wider range of environments while also opening up new ways to reduce energy consumption and costs.
The second paper, from IBM, introduces a new model of quantum error correction focused on improving the performance of its superconducting quantum bit, transmon.
The third paper reveals the first experimental observation of graviton excitation by a team of scientists. This is an important experimental validation of the theory of gravitons in high-energy quantum physics, and also provides a new perspective on the connection between quantum gravity theory and condensed matter physics.
The publication of these papers demonstrates the latest developments at the frontiers of quantum technology, and also provides valuable insights into our understanding and advancement of related technological breakthroughs. Taken together, these three papers show that researchers in this field are working hard to overcome technical challenges and lay the groundwork for practical quantum applications.
Quantum processor achieves stable operation at high temperatures
However, this approach faces a significant challenge. Like many other quantum bit technologies, quantum dots must be kept at extremely low temperatures (less than one kelvin) to avoid environmental disturbances. At the same time, the traditional circuitry portion of a silicon chip generates heat when it operates, as it did in the once-popular x86 laptops.
While heat generation from conventional silicon chips is a common problem, the current leading quantum computing paradigm requires cooling the system to near absolute zero (-273.15°C). Companies like Google, IBM, and PsiQuantum are preparing for a future where cooling systems are intensive, and it is expected that running a quantum computer will require a lot of power. At higher temperatures, quantum bits tend to decay, making the technology impractical for practical applications.
However, if quantum computers can operate stably at slightly higher temperatures, they will be easier to operate and have a wider range of applications. According to the latest research published in the journal Nature on Wednesday, the problem may not be as tricky as we thought.
The Diraq team recently demonstrated the ability of their spin-based quantum processor to operate at temperatures up to 20 times higher than ever before, while maintaining its stability and high precision. This significant advancement has attracted much attention in the field of quantum computing.
The research team successfully demonstrated that a spin-based quantum calculator can maintain high-precision operation at temperatures exceeding one kelvin. This temperature range is compatible with conventional electronic devices, meaning that it is possible to run complex error-correcting programs, which is essential for reliable quantum computing. jonathan Huang, a research associate at Diraq and a PhD student at the University of New South Wales, points out that this result opens up a new path for the development of practical quantum computers.
The experiment was done on a two-qubit prototype that used materials specifically selected to increase tolerance to noise. The experimental procedure was also optimized to limit error generation. The team started the experiment with normal operation at 0.1K and gradually raised the temperature to 1.5K while monitoring its performance. They found that one of the main sources of error, state preparation and measurement (SPAM), did not change significantly over this temperature range: "SPAM around 1K is comparable to that at millikelvin temperatures, and the approach is valid at least until 1.4K. "
While the temperature difference from 15 millikelvin (0.015K) to 1 Kelvin may not sound like much, it's actually a huge leap for quantum computing. For one thing, at higher temperatures, the cooling efficiency of a dilute chiller increases significantly. Since quantum bits and their control circuits generate heat, even though the amount of heat generated by each quantum bit is insignificant, it still limits the total number of quantum bits that can be cooled by a dilution chiller. In addition, it has been estimated that at 15 milli-Kelvin, the cooling power of a dilution chiller is about 10 to 20 microwatts, so the maximum number of possible quantum bits that can be operated may be limited to about 1,500. At 1 kelvin, on the other hand, the cooling power of the chiller may be 1,000 microwatts or more, meaning that individual modules containing thousands to 100,000 quantum bits could be cooled. On the other hand, higher temperatures increase the thermal motion of electrons, which in turn generates noise and reduces the coherence of quantum bits, affecting computational accuracy.
The key, therefore, was to find a way to operate efficiently at 1 Kelvin temperatures without sacrificing the quality of the quantum bits. This is exactly what Diraq has announced it has achieved.
This achievement complements the other advantages of the spin-quantum bit technology employed by Diraq. Spin quantum bits require a much smaller chip area than other alternatives such as superconducting technology. As a result, a large number of quantum bits can be integrated on a smaller semiconductor chip.
Diraq plans to use this approach to develop large-scale quantum processors without the need for complex multi-module designs used by other companies. Key performance metrics reported by the company include up to 99.85% fidelity for single quantum bit gates, 98.92% fidelity for double quantum bit gates, and 99.34% initialization and readout fidelity. These levels are close to the levels that make error correction algorithms feasible in practical applications.
These results show that quantum calculators can operate at relatively high operating temperatures without causing problems in the on-chip control circuits.
Prof. Andrew Dzurak, CEO and founder of Diraq, emphasized that the company's innovative hardware uses a new technology called "silicon spin" to solve the challenge of scaling up millions of quantum bits in quantum computing, making Diraq stand out in the field of quantum computing. Diraq stands out in the field of quantum computing.
While our quantum processors still need to be cooled, the cost and complexity of the entire system is significantly reduced at these higher temperatures," said Dzurak. Using 'hot qubits' (hot qubit), our quantum computers will be able to outperform existing supercomputers, enabling faster and more accurate predictions and analysis, while saving cost and energy in solving global problems, bringing significant economic benefits."
The development of quantum computers is still in its infancy, and in the future they could be as common as silicon chips are today. But the path toward that future will be fraught with technical challenges.
This advancement in running quantum bits at higher temperatures is a key step in simplifying system requirements.
It holds the promise of taking quantum computing out of specialized labs and into the broader scientific, industrial and commercial realms.
Diraq's strategic goal is to become a full-service quantum computing provider, combining the current value propositions of chipmakers, cloud computing companies and software algorithm providers to unlock the full potential of quantum computing. The quantum computing industry is expected to create $450 billion to $850 billion in economic value by 2040.
IBM Reveals New Error Correction Model
However, IBM's plans are not limited to waiting until enough quantum bits are integrated to enable efficient operation of surface codes. Instead, IBM is developing a roadmap that aims to enable error-correcting quantum computing, which involves a type of logic quantum bit that requires fewer hardware quantum bits. This approach, known as "low-density parity-check codes" (LDPC), requires long-distance connections between quantum bits.
The current challenge is that IBM's existing quantum processors do not contain any long-distance connections, making it impossible to test the concept on real hardware. Nonetheless, based on the nature of its existing hardware quantum bits, IBM has conducted extensive modeling of how such a system might behave.
Tanner diagrams of surface and BB codes (IBM named the new code in this experiment bivariate bicycle)
Simulation results show that using some LDPC scheme, only 288 physical quantum bits are required to process several logical quantum bits, which is far fewer than the number of quantum bits required to implement an effective surface code (which, depending on the situation, may require about 3,000 hardware quantum bits). With reasonable hardware error rates, it has an overall error rate comparable to that of surface codes; and, with hardware improvements, the error suppression of code implementations can increase significantly, even if the probability of physical errors decreases only slightly.
Ultimately, the best system explored by IBM had an error rate of about 2 × 10^(-7), meaning that it could remain stable for several logic quantum bits over about a million error correction cycles. Schemes using more hardware quantum bits could further improve performance.
However, these are still model-based theories. In order to implement these ideas in hardware, IBM would need to make a number of adjustments. IBM would need to nearly double the number of interconnections between quantum bits compared to the current configuration. Currently, no quantum bit is connected to more than three other quantum bits. In addition, chips with longer distance connections would have to be produced.
Therefore, it may be some time before we witness the testing and validation of these theories in the real world.
First experimental observation of high-energy quantum examples
In the same period, a group of international researchers from Columbia University, Nanjing University, Princeton University and the University of Muenster published a remarkable research result in the journal Nature. They observed for the first time a collective excitation phenomenon with spin in semiconductor materials, named "chiral graviton mode" (CGM).
This phenomenon is actually a novel graviton-like quasiparticle observed in condensed matter.
A graviton is a theoretically predicted undiscovered elementary particle in high-energy quantum physics, hypothesized to be the transmission medium for gravity, a fundamental force in the universe. However, the fundamental cause of gravity remains a mystery in physics to this day. Studying graviton-like particles in a laboratory setting could help bridge the theoretical gap between quantum mechanics and Einstein's theory of relativity, solving one of the great puzzles of physics and expanding our deeper understanding of the universe.
This breakthrough in experimental technology and fundamental physics represents a major advance from zero to one. The research team independently designed and assembled a resonant inelastic polarized light scattering system at extremely low temperatures and in a strong magnetic field environment. The system can be likened to a special "telescope", up to two stories high, capable of capturing weak excitation signals with frequencies as low as 10 GHz at -273.1 degrees Celsius and determining their spins.
Prof. Du Lingjie, former postdoctoral fellow at Columbia University and current professor at the School of Physics, Nanjing University, said, "Using this advanced equipment, we have successfully observed graviton-like excitations under the fractional quantum Hall effect in a gallium arsenide semiconductor quantum well. Through resonant inelastic light scattering, we measured the lowest-energy long-wave collective excitation and observed that this excitation is characterized by spin 2 by changing the spin states of the incident and scattered light."
He further explains that these experimental results provide sufficient experimental evidence for graviton excitations from the point of view of spin, momentum and energy. This is the first time since the concept of gravitons was introduced that quasiparticles with graviton properties have been observed experimentally.
The results of this experiment open up new perspectives for the study of quantum gravity-related physics in condensed matter systems. Meanwhile, the graviton-like excitations observed in this work reveal the quantum geometry in topological order, providing key experimental evidence for new geometric theoretical aspects of the fractional quantum Hall effect. This study provides an experimental basis for the validation of fractional-state wave functions in topological quantum computation and opens up new research directions for exploring geometric effects in topologically correlated states of matter.
Prof. Du Lingjie concluded, "Our experimental results mark the first experimental verification of the concept of graviton in quantum gravity theory since the 1930s, a discovery of epochal significance in condensed matter physics."
Exploring the Unknown, Crossing Scientific Boundaries
In the current field of technology and science, rapid advances in quantum computing technology are leading us into an era of dynamism and innovation.IBM's new explorations in quantum error correction technology, the Diraq team's innovations in quantum processors, and breakthroughs in the study of gravitons each represent a deepening of existing scientific theories, while bravely exploring uncharted territory.
These results herald a move toward building more efficient and practical quantum computers, while also deepening our quest for a deeper understanding of the universe.
Of particular note is the potential for complementary and critical connections between these breakthroughs. For example, IBM's error-correction scheme could theoretically be applied to the hardware systems being developed by the Diraq research team, even though they use transmon and quantum dots, which are two completely different physical systems. In addition, the observation of gravitons, while primarily a major breakthrough in high-energy physics and basic science, may inspire new scientific questions and technological needs, which in turn may drive further development of quantum computing technology. Basic science discoveries such as these may provide new perspectives and challenges for quantum computing and drive innovations in quantum hardware and software.
While there is still much uncertainty about the overall future of quantum computing, these results demonstrate some of the illuminating research being done that seeks to build the key components needed for the future of quantum computing. It is unclear how many of these research results will be applied to future quantum technology practices, but there is reason to believe that the coming of the quantum era will herald a new era of innovation and revolutionary breakthroughs.
We are standing on the threshold of this new era, witnessing the unfolding of limitless possibilities.
