Scientists manipulate quantum light for the first time
On March 20, scientists at the University of Sydney, Australia, and the University of Basel, Switzerland, demonstrated for the first time the ability to identify and manipulate a small number of interacting photons (packets of light energy) that are highly correlated. This unprecedented achievement is an important milestone in the development of quantum technology.
More than a century ago, by observing the interaction of light with matter, scientists discovered that light is not a beam of particles or a mode of energy fluctuation, but exhibits both properties, i.e., wave-particle duality. The way light interacts with matter continues to capture the imagination of scientists and humans alike, both for its theoretical beauty and its powerful practical applications.
In 1916, Einstein laid the foundation for the laser by introducing the concept of stimulated emission. In this new study, scientists observed the stimulated emission of a single photon. Specifically, they were able to measure the direct time delay between a photon and a bound photon scattered from a single quantum dot. In this case, a quantum dot is an artificially created atom.
Quantum light is one of the important tools for studying quantum information and quantum computing, and has unique properties such as wave-particle duality and quantum entanglement, which have wide applications in communication, sensing and computing. The research and application of quantum light is important for realizing major applications such as quantum communication, quantum computing and quantum confidentiality, and is one of the hot spots in quantum information science today.
The researchers said that the results open the door for manipulating "quantum light", and this basic science research opens the way for the advancement of quantum enhanced measurement technology and optical quantum computing.
A rendering of the interaction between photons and artificial atoms
The way light interacts with matter is attracting more and more research, such as the use of light to measure small changes in distance through interferometry. However, the laws of quantum mechanics set limits on the sensitivity of such devices: between the measurement sensitivity and the average number of photons in the measuring device.
This time, the researchers said their device created a strong interaction between photons, which allowed them to observe the difference between one photon interacting with it and two. They found that the delay time of one photon was longer compared to two photons. With this very strong photon-photon interaction, the two photons become entangled in the form of two-photon bound states (two-photon bound states).
Pulse scattering related to the number of photons.
Delayed dispersion of single-photon and two-photon bound states.
Two-photon bound states as a function of the input pulse width.
The advantage of quantum light is that, in principle, it allows for more sensitive measurements at higher resolution using fewer photons. This is important for applications in biological microscopy, especially when the intensity of the light may damage the sample and when the features the scientists need to observe are very small.
This time, the experimental team demonstrated the ability to manipulate and identify highly correlated photon states in a timely manner. The results reveal the interaction of a single quantum emitter with a single photon. This achievement represents an important milestone in the development of various quantum technologies.
Stimulated emission plays a central role, for example, in the approximate quantum cloning of photons, a key technology for quantum information processing and networking. The strong dependence of the propagated pulse on the number of photons can be enhanced by cascading such cavity-QED systems and enables various important applications such as photon sequencing, photon number-resolving detectors and Bell measurements.
The revelation of two-photon bound states when interacting with individual atoms is an attractive resource for realizing high-fidelity two-quantum photon gates, such as controlled phase gates. At the same time, the same principles can be applied to develop more efficient devices to deliver photon bound states, which will have a wide range of applications in biological research, advanced manufacturing, quantum information processing, etc.
