Manipulating Quantum Laws to Create Efficient Quantum Devices and Enhancing Quantum Communication Technology

^{Credit: American Physical Society}  

 ^{By Amal Pushp, Affiliate Physicist at the Resonance Science Foundation} 

This year’s Nobel prize in physics has been awarded to three physicists for fundamental discoveries in the foundations of quantum mechanics. Specifically, it has been awarded for proving the violation of Bell’s inequalities through experiments involving the entanglement of photons, and the advancement of the science of quantum information, in general, brought about by the discoveries. RSF Physicist Dr. Ines Urdaneta has already described this year’s Nobel prize in her latest article. The reader is advised to check it out for more details.  

In this article, our focus is on the manipulation of this fundamental knowledge posed by some of the related work in the creation of efficient quantum devices. Our aim is to discuss some of the recent progress in quantum technology which apparently builds on the laws of quantum mechanics and quantum information processing. 

One of the discoveries concerns the precision of quantum measurements. In this regard, researchers from Tampere University have opened up the debate on the Gouy phase anomaly, which occurs during the focusing of light waves [1].  

Robert Fickler, who is the leader of the Experimental Quantum Optics group at Tampere University, says: "Interestingly, we started with an idea based on our earlier results and set out to structure quantum light for enhanced measurement precision. However, we then realized that the underlying physics of this application also contributes to the long debate about the origins of the Gouy phase anomaly of focused light fields". 

One of the prominent characteristics of the Gouy phase is that it can be utilised to uncover the dynamics of a light beam and the speed of quantum Gouy phase can help enhance the precision of distance measurements. 

The next quantum device in line for our discussion is photonic qubits which are essentially quantized units of information. A technological challenge with photonic qubits concerns their transmission over long distances as photons are prone to certain losses (like energy, intensity, etc) during transmission over massive distances. Another challenge is the lack of mutual interactions between photons. In order to tackle some of these challenges, researchers at the University of Copenhagen in Denmark, Instituto de Física Fundamental IFF-CSIC in Spain, and Ruhr-Universität Bochum in Germany have come up with a new method which was published in Nature Physics [2]. As described in the report by Phys.org, their method involves quantum emitters coupled with a nanophotonic waveguide in an orderly manner thus enabling nonlinear interactions between wave packets of single photons (see figure below). 

^{Two photons propagating in a waveguide interact with a single quantum emitter. The photon-photon interaction results in correlations. Image and text credit: Le Jeannic et al.} 

At last, let us look at some recent important breakthroughs in quantum communication technology. Conventionally, entanglement is one of the key principles used in the creation of secure quantum communication networks and is potentially feasible for long-distance quantum communication. For example, experimental physicist Jian-Wei Pan, who also happens to be this year’s Nobel laureate Anton Zelinger’s former student, applied quantum entanglement and displayed its distribution to two locations separated by about 1203 Km on the Earth [3]. This was achieved through a quantum satellite that had two ground stations in China, establishing a distance record for non-local correlations.   

Another solid application that plays a critical role in quantum communication technology is called QKD which stands for Quantum-Key Distribution. Interestingly, the foundations of this technology were also led and shaped by Anton Zeilinger and his colleagues. To be more specific about this work, Zelinger was one of the first to lead a research group that ultimately exhibited entanglement-based QKD [4]. This accomplishment has far-reaching consequences and in the modern era, finds its usability in cybersecurity, as it could significantly impact the security of communications. 

Thus, it is clear from our discussion here that this year’s prize in physics has turned out to be a well-deserved recognition since the foundational work is helping the quantum industry boom in numerous ways through the creation of efficient technologies. It would be interesting to see how the current trends in quantum foundations research shape the path toward quantum technological applications in various areas of scientific research ranging from medical science to cosmology. 

References 

[1] Markus Hiekkamäki et al, Observation of the quantum Gouy phase, Nature Photonics (2022). DOI: 10.1038/s41566-022-01077-w 

[2] Hanna Le Jeannic et al, Dynamical photon–photon interaction mediated by a quantum emitter, Nature Physics (2022). DOI: 10.1038/s41567-022-01720-x 

[3] Jian-Wei Pan et al, Satellite-Based Entanglement Distribution Over 1200 kilometers, Science (2017). DOI: 10.1126/science.aan3211 

[4] Anton Zeilinger et al, Quantum Cryptography with Entangled Photons, Physical Review Letters (2000). DOI: 10.1103/PhysRevLett.84.4729