Attosecond science, the laser-led study of what happens to matter over very short timescales, could lead to major advances in our understanding of nature’s fastest processes.
It could enhance the problem-solving capabilities of computers, develop more efficient solar power cells, and both identify new medical treatments and improve diagnostic processes – all vital areas of research as we look for solutions to climate change and innovative ways to combat illness.
An attosecond equates to one-billionth of one-billionth of a second. Attosecond science – the subject of the 2023 Nobel prize in physics
– involves using such almost unimaginably short, intense pulses of laser light to transfer lots of energy to a “target” material. This causes the material to emit very fast-moving electron particles along with ultraviolet and X-ray light – allowing the motion of electrons to be observed in real time.
Physicists such as myself can then measure or predict how these electrons move, something that can’t normally be done. And by making attosecond pulses even shorter, we can get more information on how the electrons behave.
Electrons are extremely small particles – the building blocks of matter – that carry energy in atoms, biomolecules (which could act as new medical drugs), nanostructures and metals. Controlling how electrons move, and capturing this in images, could completely reshape how we view and interact with nature. Attosecond science has already spawned new research in areas such as attochemistry, attobiology and attomicroscopy.
Shortening the pulse
In recent years, the laser pulses used in attosecond science have become shorter and the laser fields more intense. The world record for the shortest light pulse is 43 attoseconds, achieved at the Swiss university ETH Zurich in 2017.
This broke the record of 53 attoseconds set months earlier by researchers at the University of Central Florida, who had themselves broken the world record twice over the previous five years.
These extremely short attosecond pulses also carry more energy – especially when generated using a free-electron laser, which can reach electrons deep inside the cores of atoms that were previously inaccessible.
Attosecond science allows scientists to probe the fundamentals of quantum physics under a wider range of conditions. One team in South Korea has reported reaching laser intensities equivalent to taking “all the sunlight across the planet” and compressing it into an area “the size of a red blood cell”.
This may pave the way for creating sub-atomic particles from a vacuum using only light – giving physicists a new way to study these particles, the building blocks of matter in our universe.
In the past decade, attosecond science has also moved from its target materials being gases and small molecules to solids and organic molecules. But strong electromagnetic fields generated by the lasers can change the structure of the targets, or even destroy them – so it can be a challenging process for scientists to carry out.
In materials such as organic photovoltaics (used in solar cells), which contain carbon-based substances including plastics, electrons interact with each other and their surrounding environment when exposed to attosecond pulses.
Studying this behaviour may help scientists improve the technology in solar cells: tracking the first fractions of a second after light strikes the cell could allow the materials in it to be tweaked, boosting performance.
Attosecond science could lead to a better understanding of photosynthesis, where plants convert light energy into chemical energy to sustain life. The field could also be key to building optoelectronic computers, which have switching speeds (a measure of their responsiveness) 100,000 times faster than existing digital electronic devices.
Fast switching speeds enable a device to carry out more operations per second, so this could enable faster computers.
Quantum applications
Theoretical research about the potential to combine attosecond science with quantum computing is ongoing. In theory at least, marrying the two could enable extremely difficult calculations beyond what’s possible with conventional computers. Such devices would be enabled by several important principles from quantum physics.
One principle is “superposition”: the ability of quantum particles, such as atoms, to be in multiple quantum states at the same time. Quantum computers encode their data in particles known as qubits. So, if qubits are in superposition, this means they can crunch through an extraordinarily large number of potential solutions to a problem at once – a key advantage over conventional computers.
Another important principle is “entanglement”, where two or more sub-atomic particles become connected. This allows many qubits to act in coordinated ways, also enabling faster processing speeds.
The ultimate goal is to achieve conditions that allow quantum effects to be precisely engineered, so we can build quantum computers that have practical uses. So far, this has been achieved by trying to prevent “decoherence”, where qubits spontaneously lose their quantum properties.
But the light-induced processes and extremely short timescales in attosecond science could give us other options for achieving better control over the qubits in a quantum computer.
Recently, schemes for using attosecond pulses in small molecules to control entanglement and the coherence of qubits (so they continue to behave according to the laws of quantum physics) have been successfully demonstrated.
An integral part of my group’s work at UCL is to explore novel approaches to attosecond phenomena, developing uses for ultrafast imaging and studying quantum effects in different areas.
Such a vibrant field brings with it a healthy dose of controversy. The attosecond science community is divided into factions who disagree about several fundamental points.
To turn controversy into constructive discussions, we have co-founded the Quantum Battles Workshops, in which early-career researchers from rival groups meet online and in person to discuss contentious topics. We also run a free seminar series called Atto Fridays, with talks and discussions published on our YouTube channel.
We are lucky and honoured to have many leaders in the field – including a Nobel prize-winner or two – supporting our activities. We hope this helps push attosecond science towards breakthroughs that could have a profound affect on many areas of research.
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