#gammarays

Gravity has been making waves - literally.  Earlier this month, the Nobel Prize in Physics was awarded for the first direct detection of gravitational waves two years ago. But astronomers just announced another huge advance in the field of gravitational waves - for the first time, we’ve observed light and gravitational waves from the same source.

There was a pair of orbiting neutron stars in a galaxy (called NGC 4993). Neutron stars are the crushed leftover cores of massive stars (stars more than 8 times the mass of our sun) that long ago exploded as supernovas. There are many such pairs of binaries in this galaxy, and in all the galaxies we can see, but something special was about to happen to this particular pair.

Each time these neutron stars orbited, they would lose a teeny bit of gravitational energy to gravitational waves. Gravitational waves are disturbances in space-time - the very fabric of the universe - that travel at the speed of light. The waves are emitted by any mass that is changing speed or direction, like this pair of orbiting neutron stars. However, the gravitational waves are very faint unless the neutron stars are very close and orbiting around each other very fast.

As luck would have it, the teeny energy loss caused the two neutron stars to get a teeny bit closer to each other and orbit a teeny bit faster.  After hundreds of millions of years, all those teeny bits added up, and the neutron stars were *very* close. So close that … BOOM! … they collided. And we witnessed it on Earth on August 17, 2017.  

Credit: National Science Foundation/LIGO/Sonoma State University/A. Simonnet

A couple of very cool things happened in that collision - and we expect they happen in all such neutron star collisions. Just before the neutron stars collided, the gravitational waves were strong enough and at just the right frequency that the National Science Foundation (NSF)’s Laser Interferometer Gravitational-Wave Observatory (LIGO) and European Gravitational Observatory’s Virgo could detect them. Just after the collision, those waves quickly faded out because there are no longer two things orbiting around each other!

LIGO is a ground-based detector waiting for gravitational waves to pass through its facilities on Earth. When it is active, it can detect them from almost anywhere in space.

The other thing that happened was what we call a gamma-ray burst. When they get very close, the neutron stars break apart and create a spectacular, but short, explosion. For a couple of seconds, our Fermi Gamma-ray Telescope saw gamma-rays from that explosion. Fermi’s Gamma-ray Burst Monitor is one of our eyes on the sky, looking out for such bursts of gamma-rays that scientists want to catch as soon as they’re happening.

And those gamma-rays came just 1.7 seconds after the gravitational wave signal. The galaxy this occurred in is 130 million light-years away, so the light and gravitational waves were traveling for 130 million years before we detected them.

After that initial burst of gamma-rays, the debris from the explosion continued to glow, fading as it expanded outward. Our Swift, Hubble, Chandra and Spitzer telescopes, along with a number of ground-based observers, were poised to look at this afterglow from the explosion in ultraviolet, optical, X-ray and infrared light. Such coordination between satellites is something that we’ve been doing with our international partners for decades, so we catch events like this one as quickly as possible and in as many wavelengths as possible.

Astronomers have thought that neutron star mergers were the cause of one type of gamma-ray burst - a short gamma-ray burst, like the one they observed on August 17. It wasn’t until we could combine the data from our satellites with the information from LIGO/Virgo that we could confirm this directly.

This event begins a new chapter in astronomy. For centuries, light was the only way we could learn about our universe. Now, we’ve opened up a whole new window into the study of neutron stars and black holes. This means we can see things we could not detect before.

The first LIGO detection was of a pair of merging black holes. Mergers like that may be happening as often as once a month across the universe, but they do not produce much light because there’s little to nothing left around the black hole to emit light. In that case, gravitational waves were the only way to detect the merger.

Image Credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)

The neutron star merger, though, has plenty of material to emit light. By combining different kinds of light with gravitational waves, we are learning how matter behaves in the most extreme environments. We are learning more about how the gravitational wave information fits with what we already know from light - and in the process we’re solving some long-standing mysteries!

Want to know more? Get more information HERE.

Image request: A visually stunning composite image showing a stylized representation of the Milky Way galaxy’s center, overlaid with an ethereal, subtle glow emanating from a specific region. Include faint star trails and a sense of vastness. Imagine a universe brimming with secrets, where what we *can’t* see holds more mass than what we can. For decades, scientists have been chasing shadows in…

Cosmic Rays Quantum Computing and Gamma Rays

New Quantum Computing Threat: Cosmic Rays Gamma Rays and Quantum Computing

A recent study found that strong particles from Earth and space directly interfere with superconducting processors' sensitive quantum bits (qubits), posing a new challenge to quantum computer development. These findings suggest that Cosmic Rays Quantum Computing and gamma rays over enormous arrays of qubits are associated faults that threaten  fault-tolerant quantum computing.

This phenomena was best demonstrated by a 63-qubit chip investigation by the Beijing Academy of Quantum Information Sciences and allied Chinese organisations. They observed that high-energy particles evoke quasiparticles, fractured pairs of superconducting electrons that destabilise sensitive quantum states. These disruptions include charge-parity shifts and bit-flips.

The team found two key offenders:

Muons: Earth's upper atmosphere atoms encounter cosmic rays from deep space to form these small, fast particles. They can sneak between people and buildings.

Terrestrial gamma rays: Supernovas and radioactive decay create these strong energy explosions, which most materials can handle.

Researchers inserted muon detectors in the quantum device's dilution refrigerator to distinguish these two radiation types. Gamma rays caused 81.6% of quasiparticle bursts and muons 18.4%. Muon-induced events were unaffected, whereas lead insulation on the refrigerator dramatically reduced gamma-ray-induced ones.

Cosmo-ray muons

Origin and Nature: Cosmos-ray muons are tiny, fast particles. Cosmic Rays Quantum Computing from space impact Earth's upper atmosphere atoms, creating them. Due to their prevalence, these particles can pass through people and structures undetected.

Cosmic-ray muons hitting a superconducting quantum processor can create quasiparticle bursts (QP bursts). QP bursts simultaneously disturb multiple qubit charge parity. Broken pairs of superconducting electrons, called quasiparticles, cause bit-flip events and charge-parity shifts in qubits' unstable quantum states.

Correlated Errors: Muon impacts create correlated errors, which can cause many qubits to fail at once. Existing error correction methods presume errors are local and uncorrelated, making fault-tolerant quantum computing difficult. These methods fail when many qubits are disrupted at once, threatening reliable, long quantum calculations.

Researchers installed muon detectors in the quantum chip-containing dilution refrigerator to detect and track these events. They confirmed that certain inconsistencies matched muon collisions with these detectors. Muon QP bursts occurred every 67 seconds, according to the study.

Muons made up 18.4% of quasiparticle bursts, while terrestrial gamma rays made up 81.6%.

Shielding Effectiveness: Applying lead to the refrigerator considerably reduced gamma-ray-induced events but had no effect on muon-induced ones. This shows that lead shielding cannot totally prevent cosmic ray errors.

The results also raise doubt on Majorana qubits, which depend on stable charge-parity states and could enable fault-tolerant quantum computing. Cosmic-ray-induced charge-parity jumps may disrupt these states, threatening topologically secure systems.

Earthly gamma rays

Origin and Nature: Terrestrial gamma rays are energy explosions. Instead of cosmic-ray muons from faraway collisions, radioactive decay yields terrestrial gamma rays on Earth. They can pierce most materials and are produced by supernovas and other strong cosmic phenomena.

Superconducting quantum processors experience quasiparticle bursts (QP bursts) from terrestrial gamma rays and cosmic-ray muons. In QP bursts, broken pairs of superconducting electrons tunnelling across quantum circuits damage qubits' fragile quantum states. This causes bit-flips and charge-parity shifts.

Correlated errors, in which a particle event fails numerous qubits at once, are a major difficulty caused by these effects. Existing error correction methods assume mistakes are uncorrelated and local, making fault-tolerant quantum computing difficult. Multiple qubit interruptions render these approaches worthless, threatening the reliability of extended quantum calculations.

The researchers used in-fridge muon detectors and a 63-qubit microprocessor to differentiate muon and gamma ray effects. They observed that terrestrial gamma rays produced more QP bursts than muons. Gamma rays caused 81.6% of quasiparticle bursts, according to the study.

Effective Shielding: The study found that adding a layer of lead to the dilution refrigerator significantly reduced gamma-ray impacts. Lead shielding, developed for terrestrial gamma rays, mitigates muon-induced errors better due to its modest impact. Since laboratory materials can cause gamma-ray-induced errors, shielding would not eliminate them and would increase costs and complexity.

Why It Matters for Quantum Computing

Correlated errors—when one particle hits numerous qubits at once—are the key issue. Most quantum error correction methods assume errors are uncorrelated, local, and affect one or a few qubits. Such solutions fail when several qubits are interrupted simultaneously.

The risk of a particle hitting the array increases as quantum processors contain hundreds or thousands of qubits, making this issue more urgent. An explosion might disrupt complex quantum calculations. The paper also concerns if increasing gate fidelities or qubit coherence lengths will be enough without fixing these errors.

The findings also cast doubt on majorana qubits, which are regarded to be promising for fault-tolerant quantum computing due to their stable charge-parity states. Cosmic-ray-induced charge-parity jumps may damage topologically protected systems.

For Better Detection and Protection

Despite challenges, experts offer hope. Their multiqubit simultaneous charge-parity leap tracking method, which is sensitive to quasiparticle bursts, may also work. Scientists may be able to forecast, adjust, and detect cosmic occurrences using this technology. If a cosmic-ray strike is detected during processing, quantum error correction circuits may be redirected around the affected qubits to preserve the calculation.

Other mitigation options

Additional mitigation methods include:

Running quantum computers underground or in insulated surroundings reduces cosmic ray radiation. However, this would increase costs and complexity and not erase gamma-ray-induced flaws from lab materials.

Designing materials: The qubits' material design led to faster decay of quasiparticles than in previous investigations. Aluminium films on the Beijing team's device increase particle collection and recombination as quasiparticle traps. Chip designers may be able to reduce particle damage by intentionally building these traps and minimising quasiparticle spaces. With suitable energy gaps, materials can absorb or neutralise particle impact phonon energy waves before they reach sensitive areas.