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A growing body of research is focusing on exploring the interactions of atoms and molecules with individual quanta of light, known as photons. The field of study uses both semi-classical and quantum-mechanical physics to understand the nature of these interactions at the submicroscopic level.
In its essence, it is quantum mechanics applied to photons. One focus of the discipline has, so far, been using photons to test the numerous counter-intuitive predictions of quantum mechanics. For example, quantum optics has already used photons to deepen our knowledge of entanglement and teleportation. These areas will prove fundamental to the development of quantum information processing.
Below, the most recent developments in the field of quantum optics will be discussed.
Entanglement
A team of researchers in Austria published a paper in the journal Nature this month that outlined how a photon entangled with matter was sent across a 50 km length of optical fiber, the longest distance that had ever been achieved, or even conceived to be possible. This achievement will be significant in establishing a new paradigm for information processing, which will be essential to the development of the quantum internet.
Teleportation
In August this year, a team of Austrian and Chinese scientists achieved complex quantum teleportation for the first time. Previously, it was only a theory but researchers were able to successfully transport the quantum state of one photon to a distant one. Before this point, only two-level states, known as qubits, could be transmitted. But with the new research, scientists proved that transportation of a three-level state, known as a qutrit, was possible.
The transportation of qutrits is significant because it means that information can be communicated outside of the restrictions of binary. That is, instead of being sent as 1s or 0s, information can be sent as 1s, 0s, both, or anything in between. This high-dimensional teleportation will likely prove fundamental to the development of quantum computers in the future.
Reconfigurable Quantum Circuits
This month, an international team of researchers from institutions in Belfast, Paris, and Vienna was able to demonstrate a route towards reconfigurable optical networks using multimode fiber and advanced wavefront shaping techniques in a potentially scalable method. The creation of reconfigurable quantum circuits, which the optical networks would construct, are vital components for initiating scalable quantum technologies.
A Definitive Solution to Quantum Hacking
In November 2019, Víctor Zapatero and Marcos Curty at the University of Vigo, Spain, published a study that put forward their innovative method for solving quantum hacking. They believe theirs to be the ultimate solution.
They developed device-independent quantum key distribution (DIQKD), based on a loophole-free violation of a Bell inequality, furnished with heralding devices that signal the arriving photon before the selection of measurement settings. This enhances the achievable distance, overcoming the only limitation of the design.
Scalable Nonclassical Field Beyond the 3 dB Limit
Researchers in South Korea have demonstrated widely scalable near-Fock-state lasing at the macroscopic scale in their new study, published last month in the journal Nature.
The team devised a new method that was able to eliminate the lasing threshold by employing atoms prepared in the same superposition state. Their work also provides validation of the one-atom theory, as their study was able to reject multi-atom effects.
Sub-Poissonian photon sources that have a reduced photon number variance are important for the fields of quantum information processing, quantum foundation, quantum metrology, and quantum optical spectroscopy. However, the well-known types of available sub-Poissonian light are not fit to stabilize a highly sub-Poissonian field in single cavity mode. The results of the South Korean team’s research changes this understanding, realizing the lasing of a scalable sub-Poisson field of up to 600 photons in the cavity.
Summary
Much important, ground-breaking work is currently taking place in the field of quantum optics, with new, innovative research being released each month. We can expect more significant advancements from research in this field in the near future.
References and Further Reading
- https://phys.org/news/2019-08-complex-quantum-teleportation.html
- https://www.nature.com/articles/s41534-019-0186-3
- https://www.nature.com/articles/s41566-019-0553-9
- https://www.nature.com/articles/s41598-019-53803-0
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