Physics World Announces Top 10 Quantum Technology Advances for 2022
Quantum physicists rejoiced in October when the Nobel Committee awarded the long-awaited physics prize to Alain Aspect, John Clauser and Anton Zeilinger for their groundbreaking research on quantum entanglement. But there are many other exciting developments in 2022, and here are some of the outstanding results from Physics World in the areas of quantum sensing, quantum information, quantum computing, quantum cryptography, and fundamental quantum science [1].
01Sensing acceleration below the quantum limit
The principle of quantum mechanics states that a quantum particle can appear in more than one place at the same time; at the same time, the entanglement principle states that quantum particles experience a connection that allows the condition of one particle to determine the condition of another, even across great distances.In November, physicists at JILA in Colorado, USA, used a combination of entanglement and delocalization to suppress noise that had previously made it impossible to perceive accelerations below the so-called quantum limit [2]. This limit is set by the quantum noise of a single particle, which has long been an important constraint on the accuracy of quantum sensors.
Therefore, overcoming it is a major step forward in science and technology.
02Quantum invisible state transfer through entanglement
Transmitting quantum information from one node to another in a network is not easy. If the information is encoded in a photon and sent through an optical fiber, the loss of the fiber erodes the fidelity of the signal until it becomes unreadable. If quantum entanglement is used to transmit the information directly, it introduces other processes that also degrade the quality of the signal.
Adding a third node to the network, as physicists at QuTech in the Netherlands did in 2021, would only make the task more difficult. That's why the QuTech researchers followed up their earlier success with the impressive transmission of quantum information from the sender (Alice) to the receiver (Charlie) via an intermediate node (Bob). Although the fidelity of Alice-Bob-Charlie transmission is only 71%, this is higher than 2/3 of the classical limit, and achieving this goal requires researchers to combine and optimize several challenging experiments [3]. It is believed that there will be more relevant research progress in 2023.
03Interference-resistant quantum computing
Physical and logical quantum bits. The ion trap used in the experiment as seen through the window of the ultra-high vacuum chamber.
Noise is a huge problem in quantum science. This is as true for computing as it is for sensing and communication, which is why it is so important to correct errors caused by this noise.
In 2022, physicists made some progress in this area, but one of the most important came in May, when researchers at the University of Innsbruck in Austria and the RWTH Aachen University in Germany demonstrated for the first time a suite of fault-tolerant quantum operations. Their ion-trap quantum computer uses seven physical quantum bits to make each logical quantum bit, plus "tagged" quantum bits to indicate dangerous errors in the system. Most importantly, the error-corrected version of the system performs better than the simpler uncorrected version, illustrating the possibilities of the technique.
04Device-independent quantum key distribution
Information security is a strength of quantum cryptography, but the security of information depends only on the weakest link in the chain. In quantum key distribution (QKD), a potential weak link is the devices used to send and receive keys, which are vulnerable to traditional hacking (e.g., someone breaking into a node and tampering with the system), even if the keys themselves are secure to quantum keys. An alternative approach is to use device-independent QKD (DI-QKD), which uses measurements of Bell inequalities in photon pairs to confirm that the key generation process has not been tampered with.
In July, two independent research groups demonstrated DI-QKD experimentally for the first time [4]: in one case, 1.5 million entangled Bell pairs were generated in eight hours and 95,884 bit-long shared keys were generated using them. Although the key generation rate needs to be higher to make DI-QKD practical in real-world cryptographic networks, the proof of principle is amazing.
Among them, Jianwei Pan and his colleagues Qiang Zhang and Feihu Xu at the University of Science and Technology of China (USTC) have achieved the first international experimental demonstration of device-independent quantum key distribution (DI-QKD) in principle by developing device-independent theoretical protocols and constructing high-efficiency optical quantum entanglement systems. Pan's team achieved the first demonstration of the principle of DI-QKD based on an all-optical system with a code rate of 466 bps, and verified that the system can still generate secure quantum keys when the fiber length reaches 220 m.
05Entangled pairs of entangled electrons and photons
In this artistic representation of the experiment, a beam of free electrons (yellow) passes next to a ring-shaped microresonator (black). Evaporation between the electron and the microresonator produces a photon entangled with the electron (turquoise).
The other entangled particles in this list are identical: photons entangled with other photons, ions entangled with other ions, and atoms entangled with other atoms. But nothing in quantum theory requires such symmetry, and an emerging class of "hybrid" quantum technologies actually relies on mixing things up.
Researchers led by Armin Feist of the Max Planck Institute for Multidisciplinary Research in Germany showed in August that they can entangle electrons and photons using a ring-shaped optical microresonator and a beam of high-energy electrons passing through the ring in a tangent line. The technique can be applied to a quantum process known as "heralding," in which the detection of one particle in an entangled pair indicates that another particle is available for a quantum circuit. This is a great example of how today's fundamental advances can drive tomorrow's innovations.
06Quantum invisible state transfer opens up space-time wormholes
The spacetime equivalent of a wormhole has been created on a quantum processor. in November, physicists announced a first-of-its-kind "quantum gravity on a chip experiment," in the words of Caltech team leader Maria Spiropulu, in which they ran a "wormhole invisibility transfer protocol" on Google's Sycamore quantum computer in such a way as to manipulate the flow of quantum information from the computer through a wormhole between two points in space-time. They ran a "wormhole invisible transfer protocol" on Google's Sycamore quantum computer, manipulating the flow of quantum information in the computer in such a way that it is mathematically equivalent or dual to information passing through a wormhole between two points in space-time.
Holographic wormholes have generated divergent opinions among physicists and general readers. Some physicists argue that the quantum simulation is too condensed compared to the theoretical model on which it is based to have a holographic dual description like a wormhole. Many believe that the physicists behind the work, and the journalists covering it, should have done a better job of emphasizing that this is not a real wormhole; in fact, to open a wormhole in real space-time would require negative energy material - which does not seem to exist.
Beyond that, there are many other technological advances of interest in 2022. For example, a team in Italy and France who hardened the indistinguishability of indistinguishable photons [5], an international team using quantum violations of classical causality to better understand the nature of causality [6], and a pair of intrepid physicists at the University of Edinburgh, UK, who showed that quantum signals would be a good way for technologically advanced aliens to establish contact over interstellar distances [7] ......
In 2023, we expect that there will be more breakthroughs and advances in the quantum field.
Reference links：
[1]https://physicsworld.com/a/quantum-science-and-technology-our-favourite-research-in-2022/
[2]https://physicsworld.com/a/double-dose-of-quantum-weirdness-pushes-sensors-past-the-limit/
[3]https://physicsworld.com/a/quantum-teleportation-expands-beyond-neighbouring-nodes/
[4]https://physicsworld.com/a/device-independent-qkd-brings-unhackable-quantum-internet-closer/
[5]https://physicsworld.com/a/quantum-teleportation-opens-a-wormhole-in-spacetime/
[6]https://physicsworld.com/a/experiments-with-quantum-cause-and-effect-reveal-hidden-nonclassicality/
[7]https://physicsworld.com/a/aliens-could-use-quantum-signals-to-communicate-with-earth/
