Early computer oscillator could become a core part of quantum computers

Aug 29, 2014
Figure 1: The parametric phase-locked oscillator (PPLO) was introduced as the ‘parametron’ in the 1950s and consisted of a simple combination of capacitors and inductors. Credit: algre/iStock/Thinkstock

At the dawn of the era of solid-state electronics, a variety of promising technologies were competing to supplant the then-ubiquitous vacuum tube. The transistor quickly proved to be the fastest and most practical of these technologies. Yet as demonstrated by Zhirong Lin and Tsuyoshi Yamamoto from the RIKEN Center for Emergent Matter Science and their colleagues, one of the abandoned solid-state technologies, the parametric phase-locked oscillator (PPLO), could enjoy a revival as a core component of quantum computers.

The PPLO, a technology used since the early development of digital computers more than half a century ago, is based on a simple resonant circuit consisting of two active components, typically an inductor and a capacitor. When the strength of one of these components was tuned very rapidly, the PPLO would begin to oscillate in a way that allowed digital information to be encoded in two stable oscillation states. PPLOs were used in some early Japanese computers, but the transistor eventually won out due its superior speed.

The ability of PPLOs to detect binary signals and store in the form of two distinct phases of oscillation makes them particularly suitable for reading the state of a quantum bit, or 'qubit'—the core element of a quantum computer. The power of a qubit is its ability to be in two or more states at once, which potentially allows for the execution of parallel computations at enormous speed. However, qubits are also notoriously fragile, and even reading a qubit's state incorrectly can corrupt the information it contains.

Lin, Yamamoto and their colleagues integrated a PPLO circuit into the measurement scheme for a superconducting qubit using a superconducting waveguide and a superconducting quantum interference device (SQUID) termination. The capacitance of the waveguide, combined with the inductance of the SQUID, created the resonant conditions necessary for the PPLO to function.

Using their PPLO circuit, the researchers were able to accurately measure the state of a qubit without destroying it. The information readout could then persist in the PPLO even if the qubit underwent a transition to a different state. The PPLO approach also proved to be significantly faster than other qubit reading schemes.

"This result opens a new field of research for PPLOs," says Lin, "and the new readout technique is a valuable addition to existing -readout methods." With further development, PPLO technology could be applied to practical quantum error-correction protocols, which are considered essential for useful, large-scale quantum computers.

Explore further: Scientists track quantum errors in real time

More information: Lin, Z. R., Inomata, K., Koshino, K., Oliver, W. D., Nakamura, Y., Tsai, J. S. & Yamamoto, T. Josephson "Parametric phase-locked oscillator and its application to dispersive readout of superconducting qubits." Nature Communications 5, 4480 (2014). DOI: 10.1038/ncomms5480

add to favorites email to friend print save as pdf

Related Stories

Combining quantum information communication and storage

Feb 14, 2013

(Phys.org)—Aalto University researchers in Finland have successfully connected a superconducting quantum bit, or qubit, with a micrometer-sized drum head. Thus they transferred information from the qubit ...

Scientists track quantum errors in real time

Jul 14, 2014

(Phys.org) —Scientists at Yale University have demonstrated the ability to track real quantum errors as they occur, a major step in the development of reliable quantum computers. They report their results ...

Progress in the fight against quantum dissipation

Apr 16, 2014

(Phys.org) —Scientists at Yale have confirmed a 50-year-old, previously untested theoretical prediction in physics and improved the energy storage time of a quantum switch by several orders of magnitude. ...

Tuning in to noisy interference

Jul 29, 2011

Establishing a detailed knowledge of the noise properties of superconducting systems is an important step towards the development of quantum computers, which will enable new types of computing. However, the ...

Recommended for you

New filter could advance terahertz data transmission

Feb 27, 2015

University of Utah engineers have discovered a new approach for designing filters capable of separating different frequencies in the terahertz spectrum, the next generation of communications bandwidth that ...

The super-resolution revolution

Feb 27, 2015

Cambridge scientists are part of a resolution revolution. Building powerful instruments that shatter the physical limits of optical microscopy, they are beginning to watch molecular processes as they happen, ...

Precision gas sensor could fit on a chip

Feb 27, 2015

Using their expertise in silicon optics, Cornell engineers have miniaturized a light source in the elusive mid-infrared (mid-IR) spectrum, effectively squeezing the capabilities of a large, tabletop laser onto a 1-millimeter ...

A new X-ray microscope for nanoscale imaging

Feb 27, 2015

Delivering the capability to image nanostructures and chemical reactions down to nanometer resolution requires a new class of x-ray microscope that can perform precision microscopy experiments using ultra-bright ...

New research signals big future for quantum radar

Feb 26, 2015

A prototype quantum radar that has the potential to detect objects which are invisible to conventional systems has been developed by an international research team led by a quantum information scientist at the University ...

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.