Home > Press > UCSB Researchers Demonstrate That 15=3x5 About Half of the Time

The device used to run the first solid state demonstration of Shor's algorithm. It is made up of four phase qubits and five superconducting resonators, for a total of nine engineered quantum elements. The quantum processor measures onequarter inch square. 
Abstract:
Computing prime factors may sound like an elementary math problem, but try it with a large number, say one that contains more than 600 digits, and the task becomes enormously challenging and impossibly timeconsuming. Now, a group of researchers at UC Santa Barbara has designed and fabricated a quantum processor capable of factoring a composite number  in this case the number 15  into its constituent prime factors, 3 and 5.
UCSB Researchers Demonstrate That 15=3x5 About Half of the Time
Santa Barbara, CA  Posted on August 20th, 2012
Although modest compared to a 600digit number, the achievement represents a milestone on the road map to building a quantum computer capable of factoring much larger numbers, with significant implications for cryptography and cybersecurity. The results are published in the advance online issue of the journal Nature Physics.
"Fifteen is a small number, but what's important is we've shown that we can run a version of Peter Shor's prime factoring algorithm on a solid state quantum processor. This is really exciting and has never been done before," said Erik Lucero, the paper's lead author. Now a postdoctoral researcher in experimental quantum computing at IBM, Lucero was a doctoral student in physics at UCSB when the research was conducted and the paper was written.
"What is important is that the concepts used in factoring this small number remain the same when factoring much larger numbers," said Andrew Cleland, a professor of physics at UCSB and a collaborator on the experiment. "We just need to scale up the size of this processor to something much larger. This won't be easy, but the path forward is clear."
Practical applications motivated the research, according to Lucero, who explained that factoring very large numbers is at the heart of cybersecurity protocols, such as the most common form of encoding, known as RSA encryption. "Anytime you send a secure transmission  like your credit card information  you are relying on security that is based on the fact that it's really hard to find the prime factors of large numbers," he said. Using a classical computer and the bestknown classical algorithm, factoring something like RSA Laboratory's largest published number  which contains over 600 decimal digits  would take longer than the age of the universe, he continued.
A quantum computer could reduce this wait time to a few tens of minutes. "A quantum computer can solve this problem faster than a classical computer by about 15 orders of magnitude," said Lucero. "This has widespread effect. A quantum computer will be a game changer in a lot of ways, and certainly with respect to computer security."
So, if quantum computing makes RSA encryption no longer secure, what will replace it? The answer, Lucero said, is quantum cryptography. "It's not only harder to break, but it allows you to know if someone has been eavesdropping, or listening in on your transmission. Imagine someone wiretapping your phone, but now, every time that person tries to listen in on your conversation, the audio gets jumbled. With quantum cryptography, if someone tries to extract information, it changes the system, and both the transmitter and the receiver are aware of it."
To conduct the research, Lucero and his colleagues designed and fabricated a quantum processor to map the problem of factoring the number 15 onto a purposebuilt superconducting quantum circuit. "We chose the number 15 because it is the smallest composite number that satisfies the conditions appropriate to test Shor's algorithm  it is a product of two prime numbers, and it's not even," he explained.
The quantum processor was implemented using a quantum circuit composed of four superconducting phase qubits  the quantum equivalents of transistors  and five microwave resonators. The complexity of operating these nine quantum elements required building a control system that allows for precise operation and a significant degree of automation  a prototype that will facilitate scaling up to larger and more complex circuits. The research represents a significant step toward a scalable quantum architecture while meeting a benchmark for quantum computation, as well as having historical relevance for quantum information and cryptography.
"After repeating the experiment 150,000 times, we showed that our quantum processor got the right answer just under half the time" Lucero said. "The best we can expect from Shor's algorithm is to get the right answer exactly 50 percent of the time, so our results were essentially what we'd expect theoretically."
The next step, according to Lucero, is to increase the quantum coherence times and go from nine quantum elements to hundreds, then thousands, and on to millions. "Now that we know 15=3x5, we can start thinking about how to factor larger  dare I say  more practical numbers," he said.
Other UCSB researchers participating in the study include John Martinis, professor of physics; Rami Barends, Yu Chen, Matteo Mariantoni, and Y. Yin, postdoctoral fellows in physics; and physics graduate students Julian Kelly, Anthony Megrant, Peter O'Malley, Daniel Sank, Amit Vainsencher, Jim Wenner, and Ted White.
####
For more information, please click here
Contacts:
Andrea Estrada
(805) 8934620
George Foulsham
(805) 8933071
Copyright © University of California  Santa Barbara
If you have a comment, please
Contact us.
Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Bookmark:
News and information
Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014
Instantstart computers possible with new breakthrough December 19th, 2014
Aculon Hires New Business Development Director December 19th, 2014
Iranian Scientists Use Nanotechnology to Increase Power, Energy of Supercapacitors December 18th, 2014
Superconductivity
Nanoscale resistors for quantum devices: The electrical characteristics of new thinfilm chromium oxide resistors that can be tuned by controlling the oxygen content detailed in the 'Journal of Applied Physics' December 9th, 2014
Unusual Electronic State Found in New Class of Unconventional Superconductors: Finding gives scientists a new group of materials to explore to unlock secrets of some materials' ability to carry current with no energy loss December 8th, 2014
Implementation of DNA Chains in Designing Nanospin Pieces November 9th, 2014
New evidence for an exotic, predicted superconducting state October 27th, 2014
Quantum Computing
Nanoscale resistors for quantum devices: The electrical characteristics of new thinfilm chromium oxide resistors that can be tuned by controlling the oxygen content detailed in the 'Journal of Applied Physics' December 9th, 2014
Electron pairs on demand: Controlled emission and spatial splitting of electron pairs demonstrated December 4th, 2014
Graphene layer reads optical information from nanodiamonds electronically: Possible read head for quantum computers December 1st, 2014
University of Minnesota engineers make sound loud enough to bend light on a computer chip: Device could improve wireless communications systems November 28th, 2014
Discoveries
Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014
Instantstart computers possible with new breakthrough December 19th, 2014
Creation of 'Rocker' protein opens way for new smart molecules in medicine, other fields December 18th, 2014
Iranian Scientists Use Nanotechnology to Increase Power, Energy of Supercapacitors December 18th, 2014
Announcements
Oregon researchers glimpse pathway of sunlight to electricity: Collaboration with Lund University uses modified UO spectroscopy equipment to study 'maze' of connections in photoactive quantum dots December 19th, 2014
Instantstart computers possible with new breakthrough December 19th, 2014
Aculon Hires New Business Development Director December 19th, 2014
Iranian Scientists Use Nanotechnology to Increase Power, Energy of Supercapacitors December 18th, 2014