Want the best quantum computers? Then you’ll need time crystals...

Martyn Warwick
By Martyn Warwick

Aug 23, 2022

  • Time crystals exist in the four dimensions of space time
  • They permit perpetual motion and negate entropy in a closed system 
  • Today they will only work at close to absolute zero, but room-temperature systems are getting closer 
  • It seems that not “everything put together sooner or later falls apart”

Lieutenant Commander Montgomery ‘Scotty’ Scott, Chief Engineer and third in command of the starship Enterprise’ had his dilithium crystals: Quantum computers could soon have time crystals. It all sounds very Doctor Who, but time crystals were theoretically predicted 10 years ago, and ongoing research now shows they can be engineered to interconnect, not only to help build quantum computers but also provide greatly improved and highly stable memory storage for the devices.  

Mind you, as of today, they’d be difficult to manage because any connections would have to take place in a superfluid of helium-3 maintained at a temperate of one-ten-thousandth of a degree above absolute zero, which itself is minus 273 degrees Celsius, so your average fridge won’t be of much use. At such a low temperature there is no viscosity, no friction and no heat is produced, and thus perpetual motion becomes a possibility. Superfluidity can occur in helium-3 when individual atoms pair up to make bosonic complexes called Cooper pairs: You’ll have to take my word for that, or read it up yourselves. 

In ‘normal’ crystals – salt, sugar or snowflakes, for example – atoms are arranged periodically in a lattice formation. These atoms move in three dimensions within that framework (up and down, left and right, backwards and forwards on an X, Y, Z axis), oscillating until, when at ground state (when all electrons are at the lowest possible energy levels), they stop moving. The structures of atoms in time crystals are very different because they oscillate in time as well in space – in other words, in a fourth dimension. And, here’s the astonishing bit, they do exhibit perpetual motion, jiggling around forever without the need for any energy input or losing any energy at any time.

By doing this, time crystals might appear to break the Second Law of Thermodynamics by negating entropy, which can be described as a measure of randomness, uncertainty, unpredictability and decline into disorder. Or, as Paul Simon sings (on his under-rated and under-played track), “everything put together sooner or later falls apart”. Entropy is also a measure of the number of possible arrangements the atoms in a system can have. However, time crystals existing in space time cannot create infinite energy as, in fact, they do obey the Second Law of Thermodynamics, because the energy is conserved within a closed system.

That negation of entropy in a closed system is down to a principle of quantum mechanics called “many-object localisation”. Here, when a force is exerted on one atom, that force is felt by that single atom alone and not by any others, i.e. the change is localised rather than systemwide. Thus, the system does not experience entropy and so become unpredictable and liable to breakdown, but instead continues to oscillate, presumably for ever (as no one ever looks at what is going on). If that happens, the state changes according to the Heisenberg uncertainty principle, which says that when a quantum system is observed and measured, its quantum wave function disappears. Thus, time crystals can work properly only when completely separate to, and isolated from, their surroundings, and then we are back to the closed system again.

A research fellow and physics lecturer at Lancaster University, Samuli Autti, has been working with scientists at Aalto University in Finland (where he completed his PhD) and created two time crystals that paired and interacted with one another. The pairing existed for 1,000 seconds, a period that equated to many billions of periods of oscillation before the wave function decayed and slowed. The research programme continues, and pairing times are expected be extended.

The experiment showed that the paired time crystals (and their interaction) may well turn out to be the basic foundation upon which to build a fully-functioning quantum computer. That’s because a mass of paired time crystals could be made to operate as qubits – ‘quantum bits’ that can represent a 1 and 0 and on and off simultaneously, to provide massive and very fast computing processing speed. Meanwhile, the search is on to develop time crystals that will work at room temperature, a breakthrough that would make it far easier to construct and run quantum computers. 

Even though the experiments may sound like something from science fiction, they are science fact, and Scotty has been proved right in his oft-repeated assertion that “Ye cannae break the laws of physics, Captain.” And, indeed, you can’t, but it may be possible to bend them a bit from time to time.

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