In a groundbreaking use of teleportation, critical units of a quantum processor have been successfully spread across multiple computers, proving the potential of distributing quantum modules without compromising on their performance.
While the transfer only took place over a space of two meters (about six feet) in an Oxford University laboratory, the leap was more than enough to emphasize the feasibility of scaling quantum technology by teleporting quantum states across an ‘internet’ of connected systems.
Teleportation is a quirk of physics that only makes sense through a quantum lens, where objects exist in a blur of possible characteristics until processes of measurement force them to adopt each state.
By mingling the undecided states of different objects in an act known as entanglement, and then carefully choosing the right kinds of measurements to make on one, it’s possible to use the answers to force an entangled object some distance away to adopt (and destroy) the original object’s quantum identity.
It might not be the kind of teleportation that would beam passengers through the vacuum of space in a blink, but it’s perfect for sharing the blur of information necessary for logical operations in a quantum processor.
“Previous demonstrations of quantum teleportation have focused on transferring quantum states between physically separated systems,” says lead author Dougal Main, a physicist at Oxford University.
“In our study, we use quantum teleportation to create interactions between these distant systems.”
Where classical computers use binary ‘on or off’ switches to perform strings of computations on bits of information, quantum computers use mathematically complex distributions of possibilities known as qubits, typically represented in a simple feature of an uncharged particle such as a charged atom.
To make this process practical, hundreds or even thousands of such particles need to have their yet-to-be-decided states entangled with one another in a restricted fashion, without intrusive objects weaving their own possibilities in and messing up the calculations.
Scaling current technology to this level is complicated by obstacles that require error-correcting processes or shielding to preserve the delicate quantum states long enough for them to be measured.
Linking a number of smaller processors across a network to create a kind of quantum supercomputer is another solution. While quantum information can be transmitted in the form of a light wave, the potential for its state to be irreversibly corrupted along the way makes it an impractical option.
Teleportation requires the receipt of measurements the old-fashioned way – through reliable binary data. Once sent, operations at the receiving end can tweak their own entangled particle until it effectively looks like the original.
The all-important quantum blur of the teleported spin state in the Oxford University experiment was an 86 percent match with the original, more than good enough for it to serve as a logic gate for a simple operation known as a Grover’s algorithm, which succeeded with 71 percent efficiency across the two quantum processors.
“By interconnecting the modules using photonic links, our system gains valuable flexibility, allowing modules to be upgraded or swapped out without disrupting the entire architecture,” says Main.
Having options for restructuring a quantum network could diversify the applications for such technology, repurposing networks of computers into tools that can measure and test physics at its most fundamental level.
This research was published in Nature.
