There is a revolution happening in astronomy. You could say there are several. In the past ten years, exoplanet studies have advanced considerably, and the first images of supermassive black holes have been captured. Interferometry has advanced incredibly thanks to highly-sensitive instruments and the ability to share and combine data from observatories worldwide. The science of very-long baseline interferometry is opening a whole new world of possibilities.
A new quantum technique could enhance optical VLBI according to a recent study by researchers from Australia and Singapore. The Stimulated Raman Adiabatic Passage (STIRAP) allows quantum information to be transferred without losses. This technique could allow for observations into previously unavailable wavelengths. This technique could allow for more detailed studies of black holes, exoplanets, the Solar System, and the surfaces of distant stars.
The leader of the research was a research fellow at the Centre for engineered Quantum Systems at the University of Australia. She was joined by a professor of theoretical physics with the Department of Electrical and Computer Engineering and the Centre of Quantum Technologies at the National University of Singapore, and a senior research fellow with the Centre of Quantum Technologies.
Interferometry is a technique that combines light from various telescopes to create images of an object that would otherwise be difficult to resolve. The technique of Very Long Baseline Interferometry is used to create detailed images of black holes, quasars, pulsars, star-forming nebulae, etc. The most detailed images of Sagitarrius A*, the stars that circle the center of our galaxy, have been provided by VLBI.
The first image of a black hole and Sgr A* was captured by the event horizon telescope. Classical interferometry is hampered by a number of physical limitations, including information loss, noise, and the fact that the light obtained is generally quantum in nature. VLBI could be used for much more detailed surveys. Dr. Huang told Universe Today in an email.
“Current state-of-the-art large baseline imaging systems operate in the microwave band of the electromagnetic spectrum. To realise optical interferometry, you need all parts of the intererometer to be stable to within a fraction of a wavelength of light, so the light can interfere. This is very hard to do over large distances: sources of noise can come from the instrument itself, thermal expansion and contraction, vibration and etc; and on top of that, there are losses associated with the optical elements.”
“The idea of this line of research is to allow us to move into the optical frequencies from microwaves; these techniques equally apply to infrared. We can already do large-baseline interferometry in the microwave. However, this task becomes very difficult in optical frequencies, because even the fastest electronics cannot directly measure the oscillations of the electric field at these frequencies.”
The key to overcoming these limitations is to use quantum communication techniques. Two coherent light pulse are used to transfer optical information between two quantum states. It will allow for efficient population transfers between quantum states without the usual issues of noise or loss.
In their paper, they describe how the starlight would be coupled into dark atomic states that do not emit light. The next step is to combine the light with quantum error correction, a technique used in quantum computing to protect quantum information from errors.
“To mimic a large optical interferometer, the light must be collected and processed coherently, and we propose to use quantum error correction to mitigate errors due to loss and noise in this process. Quantum error correction is a rapidly developing area mainly focused on enabling scalable quantum computing in the presence of errors. In combination with pre-distributed entanglement, we can perform the operations that extract the information we need from starlight while suppressing noise.”
The team considered a scenario where two facilities separated by long distances collect light. Each has its own set of quantum data that it prepares into some QEC code. The quantum states are imprinted onto a shared QEC code, which protects the data from noisy operations.
The signal is captured into the quantum memories via the STIRAP technique, which allows the incoming light to be coherently coupled into a non-radiative state of an atom. The ability to capture light from sources that account for quantum states would be a game-changer for interferometry. Other fields of astronomy are also being changed by these improvements.
It would be powerful enough to image small planets around nearby stars.
In the near future, the James Webb Space Telescope will use its advanced suite of instruments to study the atmospheres of exoplanets. The same is true of ground-based telescopes like the ELT. These observatories will allow Direct Imaging studies of exoplanets, yielding valuable information about their surfaces and atmospheres.
New quantum techniques will allow observatories to capture images of some of the most difficult to see objects in the Universe. The secrets that this could reveal are going to be revolutionary.
Further reading: arXiv
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