Quantum technology is bringing about a revolution in astronomy
Astronomy is undergoing a revolution.
The study of exoplanets has come a long way in the past decade; gravitational wave astronomy has emerged as a new field, and images of supermassive black holes (SMBHs) have been captured for the first time. Another related field, interferometry, has also made incredible progress. This is thanks to highly sensitive instruments and the ability to share and aggregate data from observatories around the world. In particular, very long baseline interferometry (VLBI) techniques are opening up a whole new realm of possibilities [1].
According to a recent study by Australian and Singaporean researchers [2], a new quantum technique could enhance optical very long baseline interferometry. Known as the Stimulated Raman Adiabatic Passage (STIRAP), it allows quantum information to be transmitted without loss. When applied with quantum error-correcting codes, this technique enables VLBI to observe wavelengths previously unreachable. Once integrated with next-generation instruments, the technology could allow for more detailed studies of the surfaces of black holes, exoplanets, solar systems and distant stars.
The research was led by Chinese Zixin Huang, a postdoctoral researcher at the Centre for Engineered Quantum Systems (EQuS) at Macquarie University in Sydney, Australia. She is also working with Gavin Brennan, Professor of Theoretical Physics at the Department of Electronic and Computer Engineering and Centre for Quantum Technology at the National University of Singapore (NUS), and Yingkai Ouyang, a Senior Research Fellow at the NUS Centre for Quantum Technology.
Zixin Huang
Specifically, interferometry involves combining light from different telescopes to form an image of an object. Very long baseline interferometry refers to a special technique used in radio astronomy where signals from astronomical radio sources (black holes, quasars, pulsars, star-forming nebulae, etc.) Detailed image. In recent years, VLBI has produced the most detailed images of stars orbiting Sagittarius A* (Sgr A*), the supermassive black hole at the center of our galaxy.
Astronomers also collaborated with the Event Horizon Telescope (EHT) to capture the first image of a black hole (M87*) and Sgr A* itself. But as they point out in their study, classical interferometry is still hampered by physical limitations, including information loss, noise, and the fact that the light obtained is often quantum in nature (where photons are entangled).
By addressing these limitations, VLBI can be used for finer astronomical surveys.
Dr Huang said, "Current state-of-the-art large baseline imaging systems operate in the microwave region of the electromagnetic spectrum. To achieve optical interferometry, all parts of the interferometer need to be stabilized to within a fraction of the wavelength of light so that light can interfere But that's hard to do at large distances: noise sources can come from the instrument itself, thermal expansion and contraction, vibration, etc.; on top of that, there are losses associated with the optics."
"The idea of this research direction is to get us from microwaves to optical frequencies; these techniques are equally applicable to infrared. We can already do large-baseline interferometry in microwaves. However, this task becomes very difficult in optical frequencies because even Even the fastest electronic devices cannot directly measure electric field oscillations at these frequencies."
An aerial view of the Paranal Observatory, showing the four 8.2-meter Unit Telescope (UT) and various installations of the VLTI. Source: ESA
The key to overcoming these limitations, Dr. Huang and her colleagues say, is the use of quantum communication techniques like stimulated Raman adiabatic channels. STIRAP involves the use of two coherent light pulses to transmit optical information between two applicable quantum states. When applied to VLBI, it will allow efficient and selective transport between quantum states without the usual noise or loss problems. The process they envision would involve coherently coupling starlight into a "dark" atomic state that does not radiate, as described in their paper "Imaging Stars with Quantum Error Correction" [2].
The next step is to combine light with quantum error correction (QEC), a technique used in quantum computing to protect quantum information from decoherence and other "quantum noise." But as Huang points out, this same technique enables more detailed and accurate interferometry. "To simulate large optical interferometers, light must be collected and processed coherently, and we propose the use of quantum error correction to mitigate errors in the process due to losses and noise. Quantum error correction is a rapidly developing field that focuses primarily on Scalable quantum computing in the presence of errors. Combined with pre-assigned entanglement, we can perform operations that extract the information we need from starlight while suppressing noise."
To test their theory, the team considered a scenario in which two far-flung facilities (Alice and Bob) collect astronomical light. Each facility shares a pre-assigned entanglement, which contains "quantum memory"; light is captured into the memory, and each facility sets its own quantum data set (qubits) into a QEC code. The received quantum state is then imprinted by a decoder on a shared QEC code, which protects the data from subsequent noise.
An overview of the STIRAP protocol proposed by Dr. Huang and colleagues.
In the "encoder" stage, the signal is captured into the quantum memory via STIRAP technology, which allows incoming light to be coherently coupled into the nonradiative states of the atoms. Taking into account the photonic capabilities of quantum states (and eliminating quantum noise and information loss) would be a breakthrough in interferometry; these improvements will also have major implications for other fields of astronomy that are being revolutionized.
"By tapping into optical frequencies, the quantum imaging network will improve imaging resolution by three to five orders of magnitude, and it will be powerful enough to detect asteroids around nearby stars, details of the solar system, the kinematics of stellar surfaces, accretion disks, and potentially The details around the black hole's event horizon are imaged. None of the known projects can solve these problems," Huang said.
In the near future, the James Webb Space Telescope (JWST) will use its suite of advanced infrared imaging instruments to characterize exoplanet atmospheres like never before.
The same is true for ground-based observatories such as the Extremely Large Telescope (ELT), the Large Magellan Telescope (GMT) and the Thirty Meter Telescope (TMT): between their large primary mirrors, adaptive optics, coronagraphs and spectrometers, these observatories will Enables direct imaging studies of exoplanets, producing valuable information about their surfaces and atmospheres.
By taking advantage of new quantum technologies and combining them with VLBI, the observatory will have another way to capture images of some of the most inaccessible and hard-to-see objects in our universe. The secrets this might reveal are sure to be revolutionary!
Reference link:
[2]https://arxiv.org/abs/2204.06044
