Canadian physicists have cracked a decades-old mystery surrounding metals that carry electricity without resistance, opening the door for everyday trains that levitate on magnetic fields, ultrapowerful quantum computers and big savings for utilities.

Details of the breakthrough in an arcane field called high-temperature superconducting are published today in the research journal, Nature.

Using uniquely pure crystals created at the University of British Columbia, researchers from the University of Sherbrooke detected an elusive signature of electrons within a high-temperature superconductor, a feat that has eluded scientists since the exotic materials were first discovered in 1986.

"This discovery has cleared the thick fog that physicists have been in for the past 20 years," said research team leader Louis Taillefer, a Sherbrooke professor previously at the University of Toronto.

Taillefer predicted the discovery would lead to room-temperature superconductors within 10 years, triggering a technological revolution similar to the invention of the transistor.

One of the most promising applications for such superconducting metals is in magnetic levitation trains, which can theoretically run at speeds of up to 500 km/h.

The force of powerful magnets suspends these trains in the air above a rail, eliminating friction from moving parts.

But the few experimental magnetic levitation (known as maglev) trains have been commercial failures because current electromagnets are too inefficient and bulky.

The use of superconducting metals for the magnets would slash both electricity costs and weight, making maglev trains practical, transportation experts say.

Other possible superconducting applications include shrinking MRI machines to the size of laptops, eliminating the 10 to 20 per cent electricity lost from resistance inside power stations and building quantum computers, machines so powerful they would make today's supercomputers resemble mere pocket calculators

The Canadian discovery of the so-called quantum oscillation signature gives physicists the key to figuring out what causes electrons in some special metals to switch to superconducting behaviour.

With that insight, they expect to be able to tweak the structure at the microscopic level to trigger superconducting behaviour at room temperatures, instead of only in the ultracold range.

"This is a key part to the puzzle of understanding how superconductivity works inside these materials," said Stephan Julian, a University of Toronto physics professor who is not a member of the research team.

Julian cautioned that it was "far from obvious" how researchers would get from this stage to room-temperature superconductors.

"These transitions are very complex things.

"It's like someone came to you and said they knew how to double the boiling point of water," he said.

The Canadian success was achieved using a high-temperature superconductor known as YBCO, which stands for yttrium barium copper oxide. Superpure YBCO crystals were grown in the University of British Columbia lab run by physicist Doug Bonn, who has been collaborating with Taillefer's group for 15 years.

That long-term collaboration was made possible through support from the Toronto-based Canadian Institute for Advanced Research, which is celebrating its 25th anniversary this year.

The YBCO crystals revealed the telltale signature after being hit with a magnetic field a million times more powerful than the Earth's natural magnetism.

That field was generated at a French government laboratory in Toulouse using a special machine overseen by Cyril Proust, who did his post-doctorate physics with Taillefer at the University of Toronto.