A team led by Robert Boyd, Canada Excellence Research Chair in Quantum Nonlinear Optics at the University of Ottawa, has successfully applied direct measurement. The recently developed method provides a new way to measure a 27‑dimensional quantum state, which is key to high security quantum communications systems. Boyd’s research was published in the November 2013 edition of Nature Communications.
Measuring a quantum state disturbs it irreversibly and does not allow for subsequent measurements. Previously, the only way to measure a 27‑dimensional quantum state was through a time‑consuming, multistage process using a technique called quantum tomography. Direct measurement is a gentler process involving the taking of two types of consecutive measurement: first a weak, gentle measurement, then a stronger one.
“Our work shows that direct measurement offers an exciting alternative to quantum tomography,” said Boyd, who is also professor of optics and physics at the University of Rochester in the United States. “As the field of quantum information continues to advance, we expect direct measurement to play an increasingly important role in this.”
Mehul Malik, lead author on the paper and a PhD in Boyd’s group when the work was performed said it is “like peeking into the box to see if Schrödinger's cat is alive, without fully opening the box.” Further information is available from Phys.org (in English only).