Feeds

Qubits turn into time travellers

Think of it as a quantum Tardis

Security for virtualized datacentres

A group of scientists from Spain’s Institute of Fundamental Physics has made the world just that little bit more weird, proposing a form of quantum entanglement that spans not just space, but time.

Physics followers will already be familiar with entanglement across space: two quanta (a pair of photons is a handy example) that have interacted in a way that gives them the same quantum state will remain entangled even though they’re in different places. Measure the quantum state of one photon, and the other photon will acquire that state apparently instantly – the “spooky action at a distance” that was one of Einstein’s objections to quantum mechanics.

Since entanglement has been repeatedly demonstrated, the world has become accustomed to the idea, even if it still seems strange, but only in the space domain. The latest research, by lead researcher Carlos Sabin (now at the University of Nottingham), Borja Peropadre, Marco del Rey, and Eduardo Martín-Martínez (now at the University of Waterloo in Canada), moves entanglement to the time domain – the entangled quanta are sharing a quantum state at different points in time.

Their work looks at the behavior of quantum fluctuations – which I have previously described in a very compressed shorthand as being the way the Universe preserves uncertainty even in a vacuum. If a bit of space is truly a complete vacuum, it’s possible to get a precise description of its state; so pairs of particles spontaneously come into existence and annihilate.

Again: quantum fluctuation seems like a too-strange-to-be-true theoretical construct, but it’s been both detected and manipulated. Moreover, the “vacuum field” is thought to contain entanglement even when it's empty (no, I don't understand how that bit works).

Sabin’s research describes how quantum electrodynamics allows a time-like entanglement. In their proposed experiment – which the researchers say can be performed with current technologies – two superconducting qubits are connected to a quantum field vacuum. In sequence, the two qubits (P for past and F for future) interact with the field – without both doing so at the same time.

(I’ve telegraphed the punch, haven’t I?) After the two interactions, P and F can become entangled without ever interacting with each other – forming a correlation that’s called “past-future entanglement”.

As the paper states, once the correlation exists, “past-future quantum correlations will have to be transferred to the qubits, even if the qubits do not coexist at the same time.”

“Qubit F interacts with the vacuum quantum fluctuations that are correlated with the vacuum quantum fluctuations that qubit P interacted with in the past,” Sabín said. “It's like if the qubits were exchanging ‘virtual’ – as opposed to real – photons, these undetectable particles propagating faster than light that are usually employed in quantum field theory to illuminate the computations.”

Published in Physical Review Letters, the paper can also be read in full at Arxiv. ®

Bootnote: As always, I don't mind being told I've slipped up in something as strange as this. ®

Internet Security Threat Report 2014

More from The Register

next story
SECRET U.S. 'SPACE WARPLANE' set to return from SPY MISSION
Robot minishuttle X-37B returns after almost 2 years in orbit
LOHAN crash lands on CNN
Overflies Die Welt en route to lively US news vid
America's super-secret X-37B plane returns to Earth after nearly TWO YEARS aloft
674 days in space for US Air Force's mystery orbital vehicle
'Utter killjoy Reg hacks have NEVER BEEN LAID', writes a fan
'Shuddit, smarty pants!' Some readers reacted badly to our last Doctor Who review ...
Experts brand LOHAN's squeaky-clean box
Phytosanitary treatment renders Vulture 2 crate fit for export
Hardened Hydrazine the source of Galileo satnav FAIL
Russian aerospace firm's kit fails on 46th mission
prev story

Whitepapers

Forging a new future with identity relationship management
Learn about ForgeRock's next generation IRM platform and how it is designed to empower CEOS's and enterprises to engage with consumers.
Win a year’s supply of chocolate
There is no techie angle to this competition so we're not going to pretend there is, but everyone loves chocolate so who cares.
Why cloud backup?
Combining the latest advancements in disk-based backup with secure, integrated, cloud technologies offer organizations fast and assured recovery of their critical enterprise data.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.