Researchers at UCSB recently demonstrated the quantum mechanical effect known as ‘entanglement’ in a demonstration of cutting edge quantum computer technology.
In a study published in the February edition of the Physical Review Letters, a collaborative of UCSB researchers displayed how their super-conducting quantum circuit could successfully generate entangled states of photons, which is the defining feature of quantum computers.
Making these states in a simple, linear system has proven difficult until now.
The UCSB researchers involved in the quantum computer technology study are postdoctoral fellows Haohua Wang and Matteo Mariantoni, and professors John Martinis and Andrew Cleland.
Described by Albert Einstein as “spooky action at a distance,” entanglement involves two particles, usually photons, coupled through the indeterminacy of some characteristic like polarization. Whatever happens to one particle immediately affects the other, even when the two are separated by great distances. In turn, researchers suggest that harnessing this technology could make communication faster than the speed of light — a real possibility in the future.
The entanglement of quantum bits — commonly referred to as qubits — makes quantum computers capable of performing unprecedented amounts of multi-tasking, rendering today’s best computers obsolete.
To conduct the study, researchers cooled two metal oscillators to just above absolute zero and then excited them using microwave pulses. Researchers were able to generate states in which all of the photons on one oscillator are in an excited state, while none are on the other. This procedure creates a situation in which qubits work together to instantly compute information.
The difficulty in making a successful and practical quantum chip is keeping the qubits from becoming thermally excited, said Jim Wenner, a fourth-year physics graduate student in Martinis’ group. Wenner was in charge of the cryogenic setup of the research, an aspect critical to the project’s success.
Daniel Sank, also a fourth-year physics graduate student of the group, described himself and the researchers as “Hamiltonian Engineers,” referring to the mathematical model that describes the underlying physics involved in building and developing open source software.
According to Sank, the development of this software may be of global importance since other groups around the world are using it.
Researchers hope to improve the number of entangled qubits to a few dozen, a number considered to be competitive with contemporary computers. However, according to Sank, the qubit is limited by the frequency stability.
In the future, increasingly qubit stability is critical to the development and application of this software and may lead to the next generation of devices.