Last updated February 15, 2018 at 11:01 am
Empty space might appear empty, but strike it with enough energy and you can ‘break’ the vacuum and create particles from nothing.
The most powerful laser in the world, the Shanghai Superintense Ultrafast Laser Facility (SULF), is planned to burst into life later this year when it attempts to reach a power level equivalent to 1,000 times the entire world’s electricity grid combined.
But reaching such extraordinary power levels will not consume the world’s electricity as that laser light shines for less than a trillionth of a second.
While extraordinarily ambitious, SULF has good reason to be confident as in 2016 it broke the world record with a laser pulse of 5.3 petawatts (PW) of power – that’s 5.3 thousand million million watts.
It achieves this by focussing just a few 100 joules of energy from a single titanium-doped sapphire crystal the size of a frisbee into a tiny fraction of a second.
Einstein’s famous E=mc2 equation
As power is energy divided by time, that modest energy is compressed into just tens of femtoseconds (10-15 of a second) allowing it to achieve a vacuum-ripping 10 PW of power for the briefest of moments.
When you reach such extraordinary levels of power the very vacuum itself can “break”, creating particles from empty space.
This is a result of Einstein’s famous E=mc2 equation, in which energy can be turned into mass (and vice versa, as is the case of nuclear explosions).
Enough energy is focussed that an electron, and it’s antimatter counterpart, the positron, can be formed.
This reaction allows researchers to explore the realm of Quantum Electrodynamics (QED) and is of great interest on pushing lasers to ever higher powers.
We can explore QED in this way thanks to a counterintuitive quantum mechanical picture of empty space, it’s actually seething with virtual particles.
Heisenberg Uncertainty principle
These virtual particles are produced as matter-antimatter pairs and are essentially created “on loan” from the vacuum, rapidly colliding and returning this borrowed energy back to the vacuum.
The Heisenberg Uncertainty principle in Quantum Mechanics states that a lot of energy, enough to generate an electron and positron, can exist for a short amount of time.
The end result is a seething mass of particles coming in and out of existence for brief periods in apparently empty space.
When these particles are illuminated by a powerful enough laser, the electrical field of the laser acts to push the particle pairs apart, as they have opposite charges.
This drains the laser pulse of some energy, effectively turning these virtual particles into real particles.
Extreme Light Infrastructure
However, this same process can limit the power of next generation lasers.
The particles in turn are accelerated and they emit energetic light, which creates yet more particle pairs, draining yet more laser light and creating a runaway avalanche of millions of particles.
This effect will in practice limit the maximum laser intensity possible, and one estimate is that the avalanche can reach just 1024 W/cm2, only 100 times the current SULF limit.
With Europe’s Extreme Light Infrastructure coming online in the next few years, the SULF team will soon have company in the 10 PW club, so SULF is racing to the ultimate vacuum-ripping limits.
CERN’s Large Hadron Collider
In 2023 the team aims to have reached 100 PW lasers with the Station of Extreme Light (SEL), at cost of $100 million, housed in a chamber 20 metres underground.
Such high-powered lasers might even replace traditional particle colliders such as the successor to CERN’s Large Hadron Collider, the 30 kilometre electron-positron collider.
For now, the SULF team will be content to break their own world record all with an eye to future records, firmly establishing Chinese dominance at vacuum-breaking level for these briefest of moments.