Nav: Home

New, better way to build circuits for world's first useful quantum computers

June 27, 2016

The era of quantum computers is one step closer as a result of research published in the current issue of the journal Science. The research team has devised and demonstrated a new way to pack a lot more quantum computing power into a much smaller space and with much greater control than ever before. The research advance, using a 3-dimensional array of atoms in quantum states called quantum bits -- or qubits -- was made by David S. Weiss, professor of physics at Penn State University, and three students on his lab team. He said "Our result is one of the many important developments that still are needed on the way to achieving quantum computers that will be useful for doing computations that are impossible to do today, with applications in cryptography for electronic data security and other computing-intensive fields."

The new technique uses both laser light and microwaves to precisely control the switching of selected individual qubits from one quantum state to another without altering the states of the other atoms in the cubic array. The new technique demonstrates the potential use of atoms as the building blocks of circuits in future quantum computers.

The scientists invented an innovative way to arrange and precisely control the qubits, which are necessary for doing calculations in a quantum computer. "Our paper demonstrates that this novel approach is a precise, accurate, and efficient way to control large ensembles of qubits for quantum computing," Weiss said.

The paper in Science describes the new technique, which Weiss's team plans to continue developing further. The achievement also is expected to be useful to scientists pursuing other approaches to building a quantum computer, including those based on other atoms, on ions, or on atom-like systems in 1 or 2 dimensions. "If this technique is adopted in those other geometries, they would also get this robustness," Weiss said.

To corral their quantum atoms into an orderly 3-D pattern for their experiments, the team constructed a lattice made by beams of light to trap and hold the atoms in a cubic arrangement of five stacked planes -- like a sandwich made with five slices of bread -- each with room for 25 equally spaced atoms. The arrangement forms a cube with an orderly pattern of individual locations for 125 atoms. The scientists filled some of the possible locations with qubits consisting of neutral cesium atoms -- those without a positive or a negative charge. Unlike the bits in a classical computer, which typically are either zeros or ones, each of the qubits in the Weiss team's experiment has the difficult-to-imagine ability to be in more than one state at the same time -- a central feature of quantum mechanics called quantum superposition.

Weiss and his team then use another kind of light tool -- crossed beams of laser light -- to target individual atoms in the lattice. The focus of these two laser beams, called "addressing" beams, on a targeted atom shifts some of that atom's energy levels by about twice as much as it does for those of any of the other atoms in the array, including those that were in the path of one of the addressing beams on its way to the target. When the scientists then bathe the whole array with a uniform wash of microwaves, the state of the atom with the shifted energy levels is changed, while the states of all the other atoms are not.

"We have set more qubits into different, precise quantum superpositions at the same time than in any previous experimental system," Weiss said. The scientists also designed their system to be very insensitive to the exact details of the alignments or the power of those light beams they use -- which Weiss said is a good thing because "you don't want to be dependent upon exactly what the intensity of the light is or exactly what the alignment is."

One of the ways that the scientists demonstrated their ability to change the quantum state of individual atoms was by changing the states of selected atoms in three of the stacked planes within the cubic array in order to draw the letters P, S, and U -- the letters that represent Penn State University. "We changed the quantum superposition of the PSU atoms to be different from the quantum superposition of the other atoms in the array," Weiss said. "We have a pretty high-fidelity system. We can do targeted selections with a reliability of about 99.7%, and we have a plan for making that more like 99.99%."

Among the goals that Weiss has for his team's future research is to get the qubits to "have entangled quantum wave functions where the state of one particle is implicitly correlated with the state of the other particles around it." Weiss said that this entangled connection between qubits is a critical element needed for quantum computing. He said he hopes that building on the techniques demonstrated in his team's prototype system eventually will enable his lab to demonstrate high-quality entangling operations for quantum computing. "Filling the cube with exactly one atom per site and setting up entanglements between atoms at any of the sites that we choose are among our nearer-term research goals," Weiss said.


In addition to Weiss, the other members of the Penn State research team are Yang Wang, Aishwarya Kumar, and Tsung-Yao Wu, all graduate students. The research was funded by the U.S. National Science Foundation.


David Weiss:, (+1) 814-863-3076
Barbara Kennedy (PIO):, (+1) 814-863-4682

Penn State

Related Quantum Computing Articles:

New method could enable more stable and scalable quantum computing, Penn physicists report
Researchers from the University of Pennsylvania, in collaboration with Johns Hopkins University and Goucher College, have discovered a new topological material which may enable fault-tolerant quantum computing.
Stanford team brings quantum computing closer to reality with new materials
Quantum computing could outsmart current computing for complex problem solving, but only if scientists figure out how to make it practical.
Computing -- quantum deep
In a first for deep learning, an Oak Ridge National Laboratory-led team is bringing together quantum, high-performance and neuromorphic computing architectures to address complex issues that, if resolved, could clear the way for more flexible, efficient technologies in intelligent computing.
Legacy of brilliant young scientist is a major leap in quantum computing
Researchers from the University of Bristol and Université Libre de Bruxelles have theoretically shown how to write programs for random circuitry in quantum computers.
WSU mathematician breaks down how to defend against quantum computing attacks
WSU mathematician Nathan Hamlin is the author of a new paper that explains how a code he wrote for a doctoral thesis, the Generalized Knapsack Code, could thwart hackers armed with next generation quantum computers.
Protecting quantum computing networks against hacking threats
As we saw during the 2016 US election, protecting traditional computer systems, which use zeros and ones, from hackers is not a perfect science.
Electron-photon small-talk could have big impact on quantum computing
In a step that brings silicon-based quantum computers closer to reality, researchers at Princeton University have built a device in which a single electron can pass its quantum information to a particle of light.
Bridging the advances in AI and quantum computing for drug discovery and longevity research
Insilico Medicine Inc. and YMK Photonics Inc. announced a research collaboration and business cooperation to develop photonics quantum computing and accelerated deep learning techniques for drug discovery, biomarker development and aging research.
New technique for creating NV-doped nanodiamonds may be boost for quantum computing
Researchers at North Carolina State University have developed a new technique for creating NV-doped single-crystal nanodiamonds, only four to eight nanometers wide, which could serve as components in room-temperature quantum computing technologies.
Exploring defects in nanoscale devices for possible quantum computing applications
Researchers at Tokyo Institute of Technology in collaboration with the University of Cambridge have studied the interaction between microwave fields and electronic defect states inside the oxide layer of field-effect transistors at cryogenic temperatures.

Best Science Podcasts 2017

We have hand picked the best science podcasts for 2017. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: Radiolab

Oliver Sipple
One morning, Oliver Sipple went out for a walk. A couple hours later, to his own surprise, he saved the life of the President of the United States. But in the days that followed, Sipple's split-second act of heroism turned into a rationale for making his personal life into political opportunity. What happens next makes us wonder what a moment, or a movement, or a whole society can demand of one person. And how much is too much?
Now Playing: TED Radio Hour

Future Consequences
From data collection to gene editing to AI, what we once considered science fiction is now becoming reality. This hour, TED speakers explore the future consequences of our present actions. Guests include designer Anab Jain, futurist Juan Enriquez, biologist Paul Knoepfler, and neuroscientist and philosopher Sam Harris.