NEC, JST and RIKEN demonstrate world's first controllably coupled qubits

May 03, 2007
Two-qubit quantum circuit with tunable coupling
Two-qubit quantum circuit with tunable coupling

NEC Corp., Japan Science and Technology Agency (JST) and the Institute of Physical and Chemical Research (RIKEN) have together successfully demonstrated the world's first quantum bit (qubit) circuit that can control the strength of coupling between qubits. Technology achieving control of the coupling strength between qubits is vital to the realization of a practical quantum computer, and has been long awaited in the scientific field.

The quantum computer, when it is finally brought to fruition, is expected to far surpass the capabilities of even the most modern of today's supercomputers. Actual computing in a quantum computer is carried out by manipulating the quantum state of qubits in time sequence by external controls. To achieve such manipulation, it is necessary to control the: 1. States of individual qubits, 2. States of two qubits (logic operation), and 3. Ability to turn on /off the coupling between qubits.

NEC, JST, and RIKEN have already announced successful development of key technologies for the world's first solid-state qubit and the world's first two-qubit logic gate, based on solid-state technology that excels in its ability to integrate qubits. Following these achievements, the research group addressed the controllable coupling of qubits as the next logical step in realization of a practical quantum computer. Their new research result represents the world's first successful demonstration of controllably coupled qubits.

To date, the coupling of qubits has been difficult to control. In order to realize this control, the research group devised an original mechanism that employs another qubit in between the two qubits for coupling. The coupling qubit functions as a non-linear transformer that is able to turn on and off the magnetic coupling between the two qubits, and on/off control is achieved simply by inputting a microwave. Moreover, coupling operation has been achieved without shortening the lifetime of each qubit. Scalability is also realized through the repetition of coupled two-qubit units - a feature necessary for future quantum computers.

To demonstrate the operation feasibility of the controllable coupling scheme, the research group employed a coupled two-qubit system, the smallest quantum logic unit, to carry out a multi-quantum control experiment involving the turning on and off of the coupling. As a result, a simple quantum protocol has been successfully demonstrated, allowing controllable coupling for the execution of quantum algorithms.

In the near future, NEC, JST, and RIKEN, plan to implement a larger-scale, more elaborate quantum computation, aiming for the realization of a practical quantum computer.

The result of this joint research will be published in the May 4th issue of the international weekly science journal, Science.

Source: NEC Corporation of America

Explore further: Penn physicists honored for work that could take heat out of computing

Related Stories

Quantum Criticality in life's proteins (Update)

Apr 15, 2015

(Phys.org)—Stuart Kauffman, from the University of Calgary, and several of his colleagues have recently published a paper on the Arxiv server titled 'Quantum Criticality at the Origins of Life'. The id ...

Recommended for you

Bringing high-energy particle detection in from the cold

May 05, 2015

Radiation detectors, which monitor high-energy particles such as those produced by nuclear decay and cosmic radiation, are being used increasingly in medical imaging, petroleum well logging, astronomy and ...

Artificial muscles created from gold-plated onion cells

May 05, 2015

Just one well-placed slice into a particularly pungent onion can send even the most seasoned chef running for a box of tissues. Now, this humble root vegetable is proving its strength outside the culinary ...

Image: Into the depths of the electromagnetic spectrum

May 05, 2015

It can be difficult in our everyday lives to appreciate the extraordinary range of wavelengths in the electromagnetic spectrum. Electromagnetic radiation—from radio waves to visible light to x-rays—travels ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.