"Ying-Yang" Photons.

Phys Org

Visualizing the mysterious dance: Quantum entanglement of photons captured in real- time

August 21 2023

Biphoton state holographic reconstruction. Image reconstruction. a, Coincidence image of interference between a reference SPDC state and a state obtained by a pump beam with the shape of a Ying and Yang symbol (shown in the inset). The inset scale is the same as in the main plot. b, Reconstructed amplitude and phase structure of the image imprinted on the unknown pump. Credit: Nature Photonics(2023). DOI: 10.1038/s41566-023-01272-3

Researchers at the University of Ottawa, in collaboration with Danilo Zia and Fabio Sciarrino from the Sapienza University of Rome, recently demonstrated a novel technique that allows the visualization of the wave function of two entangled photons, the elementary particles that constitute light, in real-time.
Using the analogy of a pair of shoes, the concept of entanglement can be likened to selecting a shoe at random. The moment you identify one shoe, the nature of the other (whether it is the left or right shoe) is instantly discerned, regardless of its location in the universe. However, the intriguing factor is the inherent uncertainty associated with the identification process until the exact moment of observation.
The wave function, a central tenet in quantum mechanics, provides a comprehensive understanding of a particle's quantum state. For instance, in the shoe example, the "wave function" of the shoe could carry information such as left or right, the size, the color, and so on.

More precisely, the wave function enables quantum scientists to predict the probable outcomes of various measurements on a quantum entity, e.g. position, velocity, etc.

This predictive capability is invaluable, especially in the rapidly progressing field of quantum technology, where knowing a quantum state which is generated or input in a quantum computer will allow to test the computer itself. Moreover, quantum states used in quantum computing are extremely complex, involving many entities that may exhibit strong non-local correlations (entanglement).

Knowing the wave function of such a quantum system is a challenging task—this is also known as quantum state tomography or quantum tomography in short. With the standard approaches (based on the so- called projective operations), a full tomography requires large number of measurements that rapidly increases with the system's complexity (dimensionality).
Previous experiments conducted with this approach by the research group showed that characterizing or measuring the high-dimensional quantum state of two entangled photons can take hours or even days. Moreover, the result's quality is highly sensitive to noise and depends on the complexity of the experimental setup.

The projective measurement approach to quantum tomography can be thought of as looking at the shadows of a high-dimensional object projected on different walls from independent directions. All a researcher can see is the shadows, and from them, they can infer the shape (state) of the full object. For instance, in CT scan (computed tomography scan), the information of a 3D object can thus be reconstructed from a set of 2D images.

In classical optics, however, there is another way to reconstruct a 3D object. This is called digital holography, and is based on recording a single image, called interferogram, obtained by interfering the light scattered by the object with a reference light.

The team, led by Ebrahim Karimi, Canada Research Chair in Structured Quantum Waves, co-director of uOttawa Nexus for Quantum Technologies (NexQT) research institute and associate professor in the Faculty of Science, extended this concept to the case of two photons.

Reconstructing a biphoton state requires superimposing it with a presumably well-known quantum state, and then analyzing the spatial distribution of the positions where two photons arrive simultaneously. Imaging the simultaneous arrival of two photons is known as a coincidence image. These photons may come from the reference source or the unknown source. Quantum mechanics states that the source of the photons cannot be identified.

This results in an interference pattern that can be used to reconstruct the unknown wave function. This experiment was made possible by an advanced camera that records events with nanosecond resolution on each pixel.

Dr. Alessio D'Errico, a postdoctoral fellow at the University of Ottawa and one of the co-authors of the paper, highlighted the immense advantages of this innovative approach, "This method is exponentially faster than previous techniques, requiring only minutes or seconds instead of days. Importantly, the detection time is not influenced by the system's complexity—a solution to the long-standing scalability challenge in projective tomography."

The impact of this research goes beyond just the academic community. It has the potential to accelerate quantum technology advancements, such as improving quantum state characterization, quantum communication, and developing new quantum imaging techniques.

The study "Interferometric imaging of amplitude and phase of spatial biphoton states" was published in Nature Photonics.

More information: Danilo Zia et al, Interferometric imaging of amplitude and phase of spatial biphoton states, Nature Photonics (2023). DOI: 10.1038/s41566-023-01272-3

See: https://phys.org/news/2023-08-visualizing-mysterious-quantum-entanglement-photons.html

Astronomers Find Two Giant Black Holes Spiraling Toward a Collision

Feb. 24, 2022

Jet Propulsion Laboratory
California Institutue of Technology

spiral black holes.jpeg

In this illustration, light from a smaller black hole (left) curves around a larger black hole and forms an almost-mirror image on the other side. The gravity of a black hole can warp the fabric of space itself, such that light passing close to the black hole will follow a curved path around it.
Credit: Caltech-IPAC

Supermassive black holes millions to billions of times the mass of our Sun lie at the heart of most galaxies, and astronomers are eager to know how these behemoths came to be. While they think most resulted from at least one merger between two smaller supermassive black holes, scientists lacked the observations that could give insight, since only one pair of supermassive black holes on the way to a merger had been found.

A new study may change that: Researchers observing a supermassive black hole report signs that it has a closely orbiting companion. The enormous duo – called a binary – circle one another about every two years.

If the team is correct, the diameter of the binary’s orbit is 10 to 100 times smaller than the only other known supermassive binary, and the pair will merge in roughly 10,000 years. That might seem like a long time, but it would take a total of about 100 million years for black holes of this size to begin orbiting one another and finally come together. So this pair is more than 99% of the way to a collision.
Joseph Lazio and Michele Vallisneri, at NASA’s Jet Propulsion Laboratory in Southern California, provided insight into how supermassive black holes behave in a binary system and how to interpret the radio data.

Evidence that this supermassive black hole may have a companion comes from observations by radio telescopes on Earth. Black holes don’t emit light, but their gravity can gather disks of hot gas around them and eject some of that material into space. These jets can stretch for millions of light-years. A jet pointed toward Earth appears far brighter than a jet pointed away from Earth. Astronomers call supermassive black holes with jets oriented toward Earth blazars, and a blazar named PKS 2131-021 is at the heart of this recent paper.

Located about 9 billion light-years from Earth, PKS 2131-021 is one of 1,800 blazars that a group of researchers at Caltech in Pasadena has been monitoring with the Owens Valley Radio Observatory in Northern California for 13 years as part of a general study of blazar behavior. But this particular blazar exhibits a strange behavior: Its brightness shows regular ups and downs as predictably as the ticking of a clock.

Researchers now think this regular variation is the result of a second black hole tugging on the first as they orbit each other about every two years. Each of the two black holes in PKS 2131-021 is estimated to be a few hundred million times the mass of our Sun. To confirm the finding, scientists will try to detect gravitational waves – ripples in space – coming from the system. The first detection of gravitational waves from black hole binaries was announced in 2016.

To confirm that the oscillations weren’t random or the cause of a temporary effect around the black hole, the team had to look beyond the decade (2008 to 2019) of data from the Owens Valley Observatory. After learning that two other radio telescopes had also studied this system – the University of Michigan Radio Observatory (1980 to 2012) and the Haystack Observatory (1975 to 1983) – they dug into the additional data and found that it matched predictions for how the blazar’s brightness should change over time.

“This work is a testament to the importance of perseverance,” said Lazio. “It took 45 years of radio observations to produce this result. Small teams, at different observatories across the country, took data week in and week out, month in and month out, to make this possible.”

See: https://www.jpl.nasa.gov/news/astronomers-find-two-giant-black-holes-spiraling-toward-a-collision

A new real-time way of visualising entangled photons – the basic particles of light – has revealed a yin-yang-like image. The technique, known as biphoton digital holography, visualised the “wave function” of the photons and was detailed in a paper published in the journal Nature Photonics last week by a team of researchers from the University of Ottawa and Sapienza University in Rome. The work comes four years after the capture of the first photo of quantum entanglement by physicists at the University of Glasgow in Scotland.

black holes orbit.jpeg

The image above i an artist's rendering of the gravitational waves given off by two circling and eventually colliding with and subsuming each other. In really, no ying and yang images of circling black holes have been seen, only the approximations of artists.


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Aug 26, 2023
Faster Quantum Computing, is generated from this, "y y", correct? There has to be somewhere in the cosmos of at least somewhat the same scale of smbh ever closer to their increased combined scale. Scary huge man! So let's give the two smbh in question 8,500 years or so? JWST found a ❓?
Aug 26, 2023
Faster Quantum Computing, is generated from this, "y y", correct? There has to be somewhere in the cosmos of at least somewhat the same scale of smbh ever closer to their increased combined scale. Scary huge man! So let's give the two smbh in question 8,500 years or so? JWST found a ❓?
Excellent amount of useful information! Thank you!
Excellent amount of useful information! Thank you!

Stanford engineers propose a simpler design for quantum computers​

A relatively simple quantum computer design that uses a single atom to manipulate photons could be constructed with currently available components.


Today’s quantum computers are complicated to build, difficult to scale up, and require temperatures colder than interstellar space to operate. These challenges have led researchers to explore the possibility of building quantum computers that work using photons — particles of light. Photons can easily carry information from one place to another, and photonic quantum computers can operate at room temperature, so this approach is promising. However, although people have successfully created individual quantum “logic gates” for photons, it’s challenging to construct large numbers of gates and connect them in a reliable fashion to perform complex calculations.

Now, Stanford University researchers have proposed a simpler design for photonic quantum computers using readily available components, according to a paper published Nov. 29 in Optica. Their proposed design uses a laser to manipulate a single atom that, in turn, can modify the state of the photons via a phenomenon called “quantum teleportation.” The atom can be reset and reused for many quantum gates, eliminating the need to build multiple distinct physical gates, vastly reducing the complexity of building a quantum computer.

“Normally, if you wanted to build this type of quantum computer, you’d have to take potentially thousands of quantum emitters, make them all perfectly indistinguishable, and then integrate them into a giant photonic circuit,” said Ben Bartlett, a PhD candidate in applied physics and lead author of the paper. “Whereas with this design, we only need a handful of relatively simple components, and the size of the machine doesn’t increase with the size of the quantum program you want to run.”

This remarkably simple design requires only a few pieces of equipment: a fiber optic cable, a beam splitter, a pair of optical switches and an optical cavity.

Fortunately, these components already exist and are even commercially available. They’re also continually being refined since they’re currently used in applications other than quantum computing. For example, telecommunications companies have been working to improve fiber optic cables and optical switches for years.

“What we are proposing here is building upon the effort and the investment that people have put in for improving these components,” said Shanhui Fan, the Joseph and Hon Mai Goodman Professor of the School of Engineering and senior author on the paper. “They are not new components specifically for quantum computation.”

A novel design

The scientists’ design consists of two main sections: a storage ring and a scattering unit. The storage ring, which functions similarly to memory in a regular computer, is a fiber optic loop holding multiple photons that travel around the ring. Analogous to bits that store information in a classical computer, in this system, each photon represents a quantum bit, or “qubit.” The photon’s direction of travel around the storage ring determines the value of the qubit, which like a bit, can be 0 or 1. Additionally, because photons can simultaneously exist in two states at once, an individual photon can flow in both directions at once, which represents a value that is a combination of 0 and 1 at the same time.

The researchers can manipulate a photon by directing it from the storage ring into the scattering unit, where it travels to a cavity containing a single atom. The photon then interacts with the atom, causing the two to become “entangled,” a quantum phenomenon whereby two particles can influence one another even across great distances. Then, the photon returns to the storage ring, and a laser alters the state of the atom. Because the atom and the photon are entangled, manipulating the atom also influences the state of its paired photon.

“By measuring the state of the atom, you can teleport operations onto the photons,” Bartlett said. “So we only need the one controllable atomic qubit and we can use it as a proxy to indirectly manipulate all of the other photonic qubits.”

Because any quantum logic gate can be compiled into a sequence of operations performed on the atom, you can, in principle, run any quantum program of any size using only one controllable atomic qubit. To run a program, the code is translated into a sequence of operations that direct the photons into the scattering unit and manipulate the atomic qubit. Because you can control the way the atom and photons interact, the same device can run many different quantum programs.

“For many photonic quantum computers, the gates are physical structures that photons pass through, so if you want to change the program that’s running, it often involves physically reconfiguring the hardware,” Bartlett said. “Whereas in this case, you don’t need to change the hardware – you just need to give the machine a different set of instructions.”

See: https://news.stanford.edu/2021/11/29/simpler-design-quantum-computers/