September 4, 2019 (updated September 4, 2019)
Published by Kshitij Kumar
A research team has demonstrated quantum enhancement in a real X-ray machine, thereby achieving the goal of elimination of background noise for precision detection. The relationship between photon pairs on quantum scales can be used to generate sharp, high-resolution images compared to classical optics. This field is called quantum imaging and has huge potential since optical light can be used to show objects that cannot be seen normally like bones and organs. Quantum correlation describes several relationships between photon pairs, among which entanglement is one and it is used in optical quantum imaging.
The technical challenges of generating entangled photons in X-ray wavelength are greater than optical light, so the team used a different approach. They used a method called quantum illumination to minimize background noise. Using parametric down-conversion (PDC), the researchers split a high energy photon into two low energy photons, signal photon, and idler photon. Researchers mentioned that the application of X-Ray PDC as a source of ghost imaging has been demonstrated recently. In previous publications, the photon statistics were not measured with any experimental evidence to date, which is generated by X-Ray PDC. Similarly, the observations of quantum enhancement sensitivity were not reported at X-ray wavelengths. The work appears in Physical Review X.
The X-Ray PDC was achieved with the help of a diamond crystal. The non-linear structure of crystal splits X-Ray photons into signal and idler beams, each having half the energy of the pump beam. The team scaled up power by using SPring-8 synchrotron in Japan. They shot a 22 KeV beam of X-rays at their crystal, splitting into two beams, carrying the energy of 11 KeV. The signal beam is sent towards the object which has to be imaged. Here, it is a small metal piece with three slits and a detector on the other side. The idler beam is directly sent to another detector so that each beam hits its respective detector at the same place and time.
The researchers then compared the detections. They found 100 correlated photons per point in the image and 10,000 background photons. Researchers could match each idler to the signal and could trace back the photons which came from the beam, thereby eliminating the noise. They later compared the images to the images developed using non-correlated photons. The correlated photons produced a sharper image.
Quantum X-ray imaging could have many uses outside current X-ray technology with a benefit of lower X-ray radiation required for imaging. This means that samples which are easily damaged by X-Rays could be imaged along with the samples with lower temperature requirement. As quantum X-Ray requires particle accelerator, there are no medical applications currently. The researchers say that they have demonstrated the ability to utilize the strong time-energy correlations of photon pairs for quantum-enhanced photodetection. The procedure they have presented possesses great potential for improving the performances of X-ray measurements.
Journal Reference: Physical Review X.
August 29, 2019 (updated August 29, 2019)
Published by Sai Teja
A team of scientists from Rochester Institute of Technology have created a new method for measuring the quantum entanglement (physical phenomenon that occurs when pairs or groups of particles are generated, interact, or share spatial proximity) that has significant consequences for building the future generation of technology in fields such as computer science, impersonation, safe communication and other areas. The new method for measuring entanglement(complexity) has been summarised by the scientists in a recently published article by Nature Communications journal.
An extraordinary interrelationship was observed in the measurements when two quantum particles like photons, electrons or atom become entangled even if the particles were apart from each other by a large distance. This special quality which can only be described by Quantum Mechanics is the backbone of the various technologies.
Gregory Howland, Assistant Professor and a member of Future Photon Initiative of Rochester Institute of Technology said that Quantum entanglement is a useful resource for performing important activities like quantum computing or secure communication. Also, he said that two people who possess entangled quantum particles can produce an unbreakable key to send messages back and forth to one another in such a way that in case if any third person or party intercepts the message, it will not be possible for them to decipher or decode the message according to laws of physics.
End-user needs to estimate the amount of quantum entanglement present within a given system as quantum technologies have become more sophisticated and complex with every passing day. The new method involving spatially entangled photon pairs needs million-times lesser measurements than the previous methods.
The measurement method has the additional advantage of never over-estimating the amount of entanglement which is present in a system as this method is based on the information theory which studies some of the key factors related to information such as quantification, storage and communication. It has been very crucial for milestone achievements such as compact disc invention, creation of the Internet, Voyager missions.
Howland said that this turns out to be vital because it is not that we are told that we have more of the resource then we actually have and this factor is mainly important for stuff like secure communication to avoid any unwanted interception of a message.
Journal Reference: Nature Communications journal
August 27, 2019 (updated August 27, 2019)
Published by Sai Teja
Quantum revolution has made it possible to sense the world in a different way. The aim is to use the unique properties of quantum mechanics to take measurements or produce images which are otherwise considered impossible.
Majority of the work is done with the help of photons. However most of the work in quantum revolution involving quantum computing, cryptography has been done with the help of visible or near-visible light.
However, Shabir Barzanjeh and his team from the Institute of Science and Technology, Austria used entangled microwaves for creating the first quantum radar in the world. It can detect far-away objects with the help of few photons thus demonstrating the stealth radars which can function without emitting detectable electromagnetic radiation. The paper can be found here.
A pair of entangled microwave photons are created with the help of a superconducting device known as Josephson parametric converter. The first photon also defined as the signal photon is beamed toward a specific object and then the reflection is captured. In the meantime, the second photon which is also called the idler photon is stored. On the arrival of the reflection, a signature is created by interfering with the idler photon which tells the distance traversed by the signal photon. A normal radar works in the similar manner, however, fails when the power levels involve lesser numbers of microwave photons. Reason being hot objects emit their own microwaves.
In-room temperature, at any instant, 1000 microwave photons are present which overwhelm the reflecting echo. So powerful transmitters are used by radar systems. This is solved in the entangled photon system. The signal and idler photons help in filtering out the effects of other photons. So it is simple to detect the signal photon upon reflection. Reflection hurts quantum entanglement since it is a fragile property, but the correlation between idler and signal photons help in distinguishing themselves from the noise.
Researchers said that a room temperature object at a distance of 1 meter was detected with the help of entangled fields using the Josephson parametric converter at millikelvin temperatures. This setup outperforms the normal radar system as it operates with lesser number of photons. But this is only for short distances.
This experiment shows the application of microwave-based entanglement and quantum radar. A potential demonstration of quantum illumination is also shown. This technique can be used in biomedical applications since it is a non-invasive scanning technique such as human tissue imaging. For a closed environment, there is the obvious application as a stealthy radar that is difficult for adversaries to detect over background noise
Journal Reference: arxiv
July 15, 2019
Published by Kalpit Veerwal
Scientists for the first time have managed to capture the first actual photo of quantum entanglement in the world. This phenomenon was so strange that Albert Einstein described it as a spooky action at a distance. This study has been published in the journal Science Advances.
This breathtaking image was captured by the scientists at the University of Glasgow in Scotland. From an aesthetic point of view, it may not look much however if it is looked at this way that this grey image is the first time we have observed the particle interaction that forms the cornerstone of quantum computing and underpins the odd science of quantum mechanics, then it is indeed very special.
Quantum entanglement takes place when two particles are so closely linked that they cannot be separated and whatever happens to one of the particles affects the other one spontaneously, irrespective of the distance between them. Thus it was described as “a spooky action at a distance“.
This image shows entanglement between two photons. They interacted for a short period of time sharing the physical states. Paul-Antoine Moreau, the first author of this paper said that the image demonstrated a very fundamental property of nature. For capturing the photo, the team of researchers made a system which blasted streams of photons entangled with each other at non-conventional objects. Then they split up the entangled photons and passed one of the beams through a liquid crystal object called β-Barium Borate, that triggered four phase transitions. They also took the photos of the entangled pair of photons simultaneously which were going through the phase transitions, although they did not pass through the liquid crystal. The camera managed to capture the images which showed that they shifted in the same direction even though they had already split up. Thus, in other words, they were entangled.
Although Albert Einstein made quantum entanglement very famous all around the globe, it was another physicist named John Stewart Bell who actually defined quantum entanglement and also established a test known as “Bell Inequality”. True quantum entanglement can be confirmed if it is possible to break the Bell Inequality.
The team mentioned in their report that in their experiment they were able to demonstrate the violation of Bell Inequality in the captured images. Thus one hand it opens up to new schemes of quantum imaging and it also promises possibilities of quantum information schemes based on spatial variables.