The shambling, shuffling, marathon march towards making a quantum computer has just skipped ahead a few steps with the first successful transference of information between two particles of matter. While earlier work with photons proved the feasibility of quantum processing, this experiment represents the first-ever creation of quantum memory.
In the experiment, University of Maryland scientists successfully teleported quantum information between two ytterbium ions suspended in special isolation traps. The scientists suspended the ions in special traps a meter apart, which then “saved” quantum data.
“It has been done before with single photons, which are really fast but very hard to store,” said Peter Maunz, a research associate and author on the paper, “But now we’ve done it with matter, now we can store information.”
Much like conventional computing, where information is stored in sequences of ones and zeroes, with a single one or zero representing one bit, quantum computing also uses discrete packets of information, called qubits. But whereas a conventional bit can only be a one or a zero, a qubit derives its power from the capacity to exist as one or a zero simultaneously.
The ability of a qubit to hold both values at the same time derives from the weirdness of quantum mechanics, the rules governing physics at a scale smaller than a single atom. According to quantum mechanics, particles like electrons or atomic nuclei don’t have defined identities until they interact with other particles.
In the experiment, Maunz and his colleagues suspended ytterbium ions into either a one or a zero state using a special frequency of microwave radiation. They then shot the ions with a laser, causing them to shuffle their state. However, since the special ion traps prevent anything from interacting with the ytterbium, and thus determining what state they shuffled into, the ions functionally held identities as both zero and one. By doing so, they formed the first qubit in history.
“If you want to think about quantum computers, at some point you need to have memory,” said Raymond Laflamme, director of the Institute for Quantum Computing, “this experiment created the first instance of quantum memory.”
Of course, one bit isn’t very useful, and Laflamme noted that at least 50 qubits would be needed before a quantum computer could perform a function that a conventional computer could not. Additionally, Laflamme said that the next step, going from two ions communicating to three ions communicating, presents a far greater challenge than what the University of Maryland scientists accomplished.
However, before moving on to that step surely difficult step, Maunz wants to make sure he can get the two ions communicating more reliably.
“The ions only communicated one every trillion times, which isn’t bad when talking about quantum mechanics” said Maunz, “but if we can get it to be successful one in a 100