In a significant breakthrough for quantum technology, researchers from the University of Basel and the University of Sydney have successfully demonstrated the ability to identify and manipulate a small number of interacting photons in a controlled manner.
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By drawing from Albert Einstein's theory of stimulated emission, the team manipulated quantum light by identifying and affecting single photons, potentially paving the way for quantum computing and medical imaging applications. The results were published in Nature Physics.
Manipulating and Identifying Interacting Photons
The light-matter has been a subject of interest for scientific research and technological development. This interaction led to the discovery of wave-particle duality, which forms the basis for various technologies, including fiber-optic cables, eyeglasses, and modern communication devices.
Photons do not interact with each other, making them ideal information carriers through optical fibers. However, for some applications in information processing, photons have to interact. This requires a nonlinear medium. When the nonlinearity is strong enough, photons can form bound states, strongly correlated and more likely to arrive together than at random times.
These bound states are not the same as bunched photon states, and researchers have predicted that the properties of photon-bound states may result in the creation of highly entangled, strongly correlated light. Photon-bound states have been predicted to exist in several systems, and experiments have observed them in strongly correlated Rydberg gases.
Advancing Stimulated Light Emission through Single Photon Manipulation
Challenges arise when manipulating the interaction between photons for certain applications, such as measuring small distance changes with interferometers. Quantum mechanics limits such devices' sensitivity, which is inversely related to the average number of photons present, meaning that higher photon counts result in reduced sensitivity.
The light-matter interaction also led to the invention of the laser, which serves as the foundation for modern technology such as GPS, global communications networks, and medical imaging. However, the requirement of a significant number of photons in stimulated light emission restricts the sensitivity of these devices.
Therefore, researchers continuously explore methods to manipulate light to interact with matter at the single photon level to overcome these limitations.
A Major Step Forward: Physicists Achieve Quantum Light Manipulation
An international team of physicists has made a groundbreaking achievement by manipulating and controlling the interaction of light particles (photons), which do not normally interact with each other. The research demonstrates stimulated light emission for single photons, a phenomenon first proposed by Albert Einstein in 1916.
"This experiment is beautiful, not only because it validates a fundamental effect—stimulated emission—at its ultimate limit, but it also represents a huge technological step towards advanced applications." Dr. Natasha Tomm, Joint Lead Author.
The researchers created a cavity in a semiconductor that contains an artificial atom (quantum dot), and when two independent photons enter the system, they emerge in a highly correlated entangled state.
The team demonstrated that a single photon traveled slower through the system than two or three-photon bound states by measuring the output power and correlation functions of a weak coherent pulse scattered off the cavity. This is due to stimulated emission, where the arrival of two photons within the lifetime of an emitter stimulates the emission of another photon.
They observed that stimulated emission involving a single quantum emitter interacting with single photons. Previously, achieving this level of control with light was challenging.
However, in this study, the team induced strong interactions between photons, enabling them to observe the difference in the time delay between a single photon and a pair of bound photons scattering off a quantum dot.
Significance of the Study
By manipulating light in a highly correlated and entangled state, more sensitive measurements can be achieved with higher resolution using fewer photons. This makes it advantageous for light-sensitive samples, such as those often found in biological microscopy, where high-intensity light can damage the samples.
This groundbreaking discovery represents a significant technological step towards developing more efficient devices that give us photon-bound states, with potential applications in various fields such as biology, quantum information processing, and advanced manufacturing.
"By demonstrating that we can identify and manipulate photon-bound states, we have taken a vital first step towards harnessing quantum light for practical use. The next steps in my research are to see how this approach can be used to generate states of light that are useful for fault-tolerant quantum computing, which is being pursued by multimillion-dollar companies, such as PsiQuantum and Xanadu." Dr. Sahand Mahmoodian, Joint Lead Author.
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References and Further Reading
Marcus Strom. (2023). Scientists Open Door to Manipulating 'Quantum Light.' [Online]. The University of Sydney. Available at: https://www.sydney.edu.au/news-opinion/news/2023/03/21/scientists-open-door-to-manipulating-quantum-light-usyd-physics.html (Accessed on 12 April 14, 2023)
Tomm, N., Mahmoodian, S., Antoniadis, N. O., Schott, R., Valentin, S. R., Wieck, A. D., ... & Warburton, R. J. (2023). Photon Bound State Dynamics from a Single Artificial Atom. Nature Physics, 1-6. https://doi.org/10.1038/s41567-023-01997-6
Xia, K. (Ed.). (2020). Single Photon Manipulation. IntechOpen. doi: 10.5772/intechopen.83207
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