Quantum Photonics.

## What Is Quantum Optics?

We investigate the quantum interaction between light and nanophotonic semiconductor materials. Our quest is to develop methods to coherently control the coupling between photons and matter utilizing tailored nanophotonic structures such as photonic crystals. Quantum Metrology. The group works with experimental setups in the laboratory, where the atoms are trapped in a magnetic field, where they are held by precise beams of laser light and are cooled down to near absolute zero, minus degrees Celsius.

The result is an atomic clock that is now so precise that it only loses one second every million years. Theoretical research. Today, experiments have advanced to a stage where one can have complete control of individual quantum systems, such as single atoms or photons. Cambridge: Cambridge University Press. Nobel Foundation. Retrieved 9 October Retrieved This audio file was created from a revision of the article " Quantum optics " dated , and does not reflect subsequent edits to the article.

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## Quantum optics

Namespaces Article Talk. Linear optics involves physical processes that conserve the total number of photons. In the ideal case, if there are photons at the beginning, no matter how complicated the physical process is, there will be exactly photons left in the end. Photons are bosonic non-interacting particles.

## Free Online Course: Introduction to Quantum Optics from Coursera | Class Central

However, they can still interference with each other, exhibiting non-trivial quantum effects. A typical example is the Hong-Ou-Mandel experiment, where two identical photons are sent to an experimental device. After a simple linear transformation, the two photons appear as if they are stuck together and unwilling to separate. In addition to providing a foundational understanding of quantum mechanics, the study of linear optics has also led to many scientific applications.

In recent years, the unique properties of linear optical systems have also inspired the development of computational complexity theory. In , Professor Scott Aaronson at MIT currently at the University of Texas at Austin proposed a linear optical method for demonstrating the quantum computational supremacy, which is based on the concept of boson sampling. More specifically, Aaronson suggested that for a class of sampling problems based on linear optical systems, it would be impossible in practice to apply any classical computer to simulate.

This idea immediately sparks a race for reaching the status of "quantum supremacy.

On the other hand, computer scientists are busy in applying supercomputers to raise the bar for achieving quantum supremacy. However, in terms of practical problems, applying the model of boson sampling is not a good approach. Recently, Prof.

Man-Hong Yung, associate professor of SUSTech and his colleagues published a paper titled " Universal bound on sampling bosons in linear optics and its computational implications " in National Science Review NSR , offering a complete solution to the open problem posed by Aaronson. Specifically, Yung's team uncovered a fundamental limit on the transition probabilities of linear optical systems, constraining the ability to transfer bosons using linear optical devices.

Together with the tools of quantum optics, they developed a classical algorithm that can efficiently estimate the transition amplitude with a bounded error. Consequently, these results lead to a negative answer to Aaronson's open problem. In other words, for encoding hard decision problems,it is necessary to make use of more complicated quantum optics systems instead of just linear optics.

As an interdisciplinary domain between quantum physics and computer science, quantum information science remains to be a highly active research area.

On one hand, the results of Yung's team contribute to the theoretical foundation of quantum optics; on the other hand, in addition to boson sampling , these results point to a novel perspective on computational complexity problems in terms of quantum optics. Undoubtedly, in the future, we should expect to see many more exciting results like these in this area. Explore further. More from Other Physics Topics. Please sign in to add a comment. Registration is free, and takes less than a minute. Read more. Your feedback will go directly to Science X editors. Thank you for taking your time to send in your valued opinion to Science X editors.

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