Researchers at <span class=”glossaryLink” aria-describedby=”tt” data-cmtooltip=”

” data-gt-translate-attributes=”[“attribute”:”data-cmtooltip”, “format”:”html”]”>USC apply strategies to control the buildup of errors, showcasing the promise of <span class=”glossaryLink” aria-describedby=”tt” data-cmtooltip=”

” data-gt-translate-attributes=”[“attribute”:”data-cmtooltip”, “format”:”html”]”>quantum computing in the error-prone NISQ era.

Daniel Lidar, the Viterbi Professor of Engineering at USC and Director of the USC Center for Quantum Information Science & Technology, and first author Dr. Bibek Pokharel, a Research Scientist at IBM Quantum, achieved this quantum speedup advantage in the context of a “bitstring guessing game.”

By effectively mitigating the errors often encountered at this level, they have successfully managed bitstrings of up to 26 bits long, significantly larger than previously possible. (For context, a bit refers to a binary number that can either be a zero or a one).

Quantum computers promise to solve certain problems with an advantage that increases as the problems increase in complexity. However, they are also highly prone to errors, or noise. The challenge, says Lidar, is “to obtain an advantage in the real world where today’s quantum computers are still ‘noisy.’”

This noise-prone condition of current quantum computing is termed the “NISQ” (Noisy Intermediate-Scale Quantum) era, a term adapted from the RISC architecture used to describe classical computing devices. Thus, any present demonstration of quantum speed advantage necessitates noise reduction.

The more unknown variables a problem has, the harder it usually is for a computer to solve. Scholars can evaluate a computer’s performance by playing a type of game with it to see how quickly an algorithm can guess hidden information. For instance, imagine a version of the TV game Jeopardy, where contestants take turns guessing a secret word of known length, one whole word at a time. The host reveals only one correct letter for each guessed word before changing the secret word randomly.

In their study, the researchers replaced words with bitstrings. A classical computer would, on average, require approximately 33 million guesses to correctly identify a 26-bit string. In contrast, a perfectly functioning quantum computer, presenting guesses in quantum superposition, could identify the correct answer in just one guess. This efficiency comes from running a quantum algorithm developed more than 25 years ago by computer scientists Ethan Bernstein and Umesh Vazirani. However, noise can significantly hamper this exponential quantum advantage.

Lidar and Pokharel achieved their quantum speedup by adapting a noise suppression technique called dynamical decoupling. They spent a year experimenting, with Pokharel working as a doctoral candidate under Lidar at USC. Initially, applying dynamical decoupling seemed to degrade performance. However, after numerous refinements, the quantum algorithm functioned as intended. The time to solve problems then grew more slowly than with any classical computer, with the quantum advantage becoming increasingly evident as the problems became more complex.

Lidar notes that “currently, classical computers can still solve the problem faster in absolute terms.” In other words, the reported advantage is measured in terms of the time-scaling it takes to find the solution, not the absolute time. This means that for sufficiently long bitstrings, the quantum solution will eventually be quicker.

The study conclusively demonstrates that with proper error control, quantum computers can execute complete algorithms with better scaling of the time it takes to find the solution than conventional computers, even in the NISQ era.

Reference: “Demonstration of Algorithmic Quantum Speedup” by Bibek Pokharel and Daniel A. Lidar, 26 May 2023, <span class=”glossaryLink” aria-describedby=”tt” data-cmtooltip=”

” data-gt-translate-attributes=”[“attribute”:”data-cmtooltip”, “format”:”html”]”>Physical Review Letters.
DOI: 10.1103/PhysRevLett.130.210602

The study was funded by the National Science Foundation and the U.S. Department of Defense.

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ESA’s exoplanet mission Cheops confirmed the existence of four warm exoplanets orbiting four stars in our Milky Way. These exoplanets have sizes between Earth and Neptune and orbit their stars closer than Mercury our Sun.

These so-called mini-Neptunes are unlike any planet in our Solar System and provide a ‘missing link’ between Earth-like and Neptune-like planets that is not yet understood. Mini-Neptunes are among the most common types of exoplanets known, and astronomers are starting to find more and more orbiting bright stars.

Mini-Neptunes are mysterious objects. They are smaller, cooler, and more difficult to find than the so-called hot Jupiter exoplanets which have been found in abundance. While hot Jupiters orbit their star in a matter of hours to days and typically have surface temperatures of more than 1000 °C, warm mini-Neptunes take longer to orbit their host stars and have cooler surface temperatures of only around 300 °C.

The first sign of the existence of these four new exoplanets was found by the NASA TESS mission. However, this spacecraft only looked for 27 days at each star. A hint to a transit – the dimming of light as a planet passes in front of its star from our viewpoint – was spotted for each star. During its extended mission, TESS revisited these stars and the same transit was seen again, implying the existence of planets.

Scientists calculated the most likely orbital periods and pointed Cheops at the same stars at the time they expected the planets to transit. During this hit-or-miss procedure Cheops was able to measure a transit for each of the exoplanets, confirming their existence, discovering their true orbital periods and taking the next step in their characterisation.

The four newly discovered planets have orbits between 21 and 53 days around four different stars. Their discovery is essential because it brings our sample of known exoplanets closer to the longer orbits that we find in our own Solar System.

One of the outstanding questions about mini-Neptunes is what they are made of. Astronomers predict that they have an iron-rocky core with thick outer layers of lighter material. Different theories predict different outer layers: Do they have deep oceans of liquid water, a puffy hydrogen and helium atmosphere or an atmosphere of pure water vapour?

Discovering the composition of mini-Neptunes is important to understand the formation history of this type of planet. Water-rich mini-Neptunes probably formed far out in the icy regions of their planetary system before migrating inwards, while combinations of rock and gas would tell us that these planets stayed in the same place as they formed.

The new Cheops measurements helped determine the radius of the four exoplanets, while their mass could be determined using observations from ground-based telescopes. Combining the mass and radius of a planet gives an estimate of its overall density.

The density can only give a first estimate of the mass of the iron-rocky core. While this new information about the density is an important step forward in understanding mini-Neptunes, it does not contain enough information to offer a conclusion for the outer layers.

The four newly confirmed exoplanets orbit bright stars, which make them the perfect candidates for a follow-up visit by the NASA/ESA/CSA James Webb Space Telescope or ESA’s future Ariel mission. These spectroscopic missions could discover what their atmospheres contain and provide a definitive answer to the composition of their outer layers.

A full characterisation is needed to understand how these bodies formed. Knowing the composition of these planets will tell us by what mechanism they formed in early planetary systems. This in turn helps us better understand the origins and evolution of our own Solar System.

The results were published in four papers: ‘Refined parameters of the HD 22946 planetary system and the true orbital period of the planet d’ by Z. Garai et al. is published in Astronomy & Astrophysics. https://www.aanda.org/10.1051/0004-6361/202345943

‘Two Warm Neptunes transiting HIP 9618 revealed by TESS & Cheops’ by H. P. Osborn et al. is published in the Monthly Notices of the Royal Astronomical Society. https://doi.org/10.1093/mnras/stad1319

‘TESS and CHEOPS Discover Two Warm Sub-Neptunes Transiting the Bright K-dwarf HD15906’ by A. Tuson et al. is published in the Monthly Notices of the Royal Astronomical Society. https://doi.org/10.1093/mnras/stad1369

‘TOI-5678 b: a 48-day transiting Neptune-mass planet characterized with CHEOPS and HARPS’ by S. Ulmer-Moll et al. is published in Astronomy & Astrophysics. https://www.aanda.org/10.1051/0004-6361/202245478

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Scientists may finally know what made the largest explosion in the universe ever seen by humankind so powerful.

Astronomers have discovered that the brightest gamma-ray burst (GRB) ever seen had a unique jet structure and was dragging an unusually large amount of stellar material along with it.

This might explain the extreme properties of the burst, believed to have been launched when a massive star located around 2.4 billion light-years from Earth in the direction of the constellation Sagitta underwent total gravitational collapse to birth a black hole, as well as why its afterglow persisted for so long.

The GRB officially designated GRB 221009A but nicknamed the BOAT, or the brightest of all time, was spotted on October 9, 2022, and stood out from other GRBs due to its extreme nature. It was seen as an immensely bright flash of high-energy gamma-rays, followed by a low-fading afterglow across many wavelengths of light.

Related: A tiny Eastern European cubesat measured a monster gamma-ray burst better than NASA. Here’s how

“GRB 221009A represents a massive step forward in our understanding of gamma-ray bursts and demonstrates that the most extreme explosions do not obey the standard physics assumed for garden variety gamma-ray bursts,” George Washington University researcher and study lead author Brendan O’Connor said in a statement. O’Connor led a team that continued to monitor the BOAT GRB with the Gemini South Telescope in Chile following its initial discovery in Oct 2023.

Northwestern University doctoral candidate Jillian Rastinejad, who was also part of a team that observed the BOAT on Oct. 14 after its initial discovery,told Live Science that GRB 221009A is thought to be brighter than other highly energetic GRBs by a factor of at least 10.

“Photons have been detected from this GRB that has more energy than theLarge Hadron Collider (LHC) produces,” she said.

Even before the BOAT was spotted, GRBs were already considered the most powerful, violent, and energetic explosions in the universe, capable of blasting out as much energy in a matter of seconds as the sun will produce over its entire around ten billion-year lifetime. There are two types of these blasts, long-duration, and short-duration, which might have different launch mechanisms, both resulting in the creation of a black hole.

Further examination of the powerful GRB has revealed that it is unique for its structure as well as its brightness. The GRB was surprisingly wide. So wide, in fact, that astronomers were initially unable to see its edges.

“Our work clearly shows that the GRB had a unique structure, with observations gradually revealing a narrow jet embedded within a wider gas outflow where an isolated jet would normally be expected,”  co-author and Department of Physics at the University of Bath scientist  Hendrik Van Eerten said in a statement.

Thus, the jet of GRB 221009A appears to possess both wide and narrow “wings” that differentiate it from the jets of other GRBs. This could explain why the afterglow of the BOAT continued to be seen by astronomers in multiple wavelengths for months after its initial discovery.

Van Eerten and the team have a theory as to what gives the jet of the BOAT its unique structure.

“GRB jets need to go through the collapsing star in which they are formed,” he said. “What we think made the difference in this case was the amount of mixing that happened between the stellar material and the jet, such that shock-heated gas kept appearing in our line of sight all the way up to the point that any characteristic jet signature would have been lost in the overall emission from the afterglow.”

Van Eerten also points out the findings could help understand not just the BOAT but also other incredibly bright GRBs.

“GRB 221009A might be the equivalent of the Rosetta stone of long GRBs, forcing us to revise our standard theories of how relativistic outflows are formed in collapsing massive stars,” O’Connor added.

The discovery will potentially lay the foundation for future research into GRBs as scientists attempt to unlock the mysteries still surrounding these powerful bursts of energy. The findings could also help physicists better model the structure of GRB jets.

“For a long time, we have thought about jets as being shaped like ice cream cones,” study co-author and George Washington University associate professor of physics Alexander van der Horst said. “However, some gamma-ray bursts in recent years, and in particular the work presented here, show that we need more complex models and detailed computer simulations of gamma-ray burst jets.”

The team’s research is detailed in a paper published in the journal Science Advances.

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