Wednesday, March 30, 2016

Russian Scientists Developed Russia’s First Two-Qubit Quantum Circuit

MIPT’s scientists develop Russia’s first two-qubit quantum circuit


A research group from MIPT’s Artificial Quantum System Laband Collective Use Center developed and tested Russia’s first superconducting two-qubit feedback-controlled circuit, an upgrade to qubit — the main component of future quantum computers — that was developed by MIPT’s scientists in 2015.

[caption id="attachment_768" align="aligncenter" width="694"]Russian Scientists Developed Russia’s First Two-Qubit Quantum Circuit                              Russian Scientists Developed Russia’s First Two-Qubit Quantum Circuit[/caption]

Modern computing components can only store one data bit at a time — 1 or 0. Qubits, as quantum objects that are in superposition of two states at a time, have the potential to store both. Moreover, they serve as an example of the so-called ‘quantum entanglement’, opening game-changing ways for data processing. A data machine made of thousands of qubits has the capacity to surpass the most powerful supercomputers in a large amount of computing tasks, such as cryptography, artificial intelligence and optimisation of complex systems.

A year ago a research group from Moscow Institute of Physics and Technology (MIPT), Institute of Solid State Physics RAS (ISSP RAS), National Institute of Science and Technology (MISIS) and Russian Quantum Center (RQC) developed Russia’s first qubit along with a parameter measuring circuit. The project success is largely based on active international collaboration. MIPT’s Artificial Quantum System Lab (AQS), headed by academic Oleg Astafiev, leads by example, within a year having established a strong and effective partnership with Royal Holloway, University of London, a leading institution in superconducting qubit research in the UK.

The two-qubit circuit is currently being developed and tested by Russian scientists from MIPT. “In the past 6 months the MIPT’s lab has done substantial and laborious work to organise the measuring process of superconducting qubits. Arguably, MIPT currently has the necessary infrastructure and human capacity to deliver on building advanced qubit systems”, comments Alexey Dmitriyev, a postgraduate at AQS.

Dmitry Negrov, Deputy Head at the Collective Use Center, says: ”We now are at the stage where system parameters are close to the designed conditions. The next step is to take vital measurements, such as coherence time and refine the qubit bonding. We aim to continue our work on these parameters in the future”.

According to Andrey Baturin, Head of Scientific Management at MIPT, quantum technology research is one of the long-term priorities on the institute’s research agenda. “The Artificial Quantum System Lab and Collective Use Center succeeded in obtaining unique equipment — modern lithographic machines and evaporation units for full-cycle production of qubits and, later, qubit systems; measuring equipment and ultra low temperature cryostats that allow us to work with qubits at the milli-Kelvin temperature range. Such low temperatures are essential due to the extreme fragility of quantum states that can easily fail from interaction with the outside environment”, says Baturin.

The development of two-qubit circuits is an important achievement that allows further field research and raises Russia’s stance in the global quantum computing race.

News Source Release : MIPT’s scientists develop Russia’s first two-qubit quantum circuit

Image Credit : Moscow Institute of Physics and Technology(MIPT)

Tuesday, March 29, 2016

Australian Researchers Create a Quantum ‘Fredkin Gate’

Unlocking the gates to quantum computing

Griffith’s Centre for Quantum Dynamics
March 28, 2016

Researchers have overcome one of the key challenges to quantum computing by simplifying a complex quantum logic operation. They demonstrated this by experimentally realising a challenging circuit, the quantum Fredkin gate, for the first time.

[caption id="attachment_762" align="aligncenter" width="468"]Australian Researchers Create a Quantum ‘Fredkin Gate’    Australian Researchers Create a Quantum ‘Fredkin Gate’[/caption]

“The allure of quantum computers is the unparalleled processing power that they provide compared to current technology,” saidDr Raj Patel from Griffith’s Centre for Quantum Dynamics.

“Much like our everyday computer, the brains of a quantum computer consist of chains of logic gates, although quantum logic gates harness quantum phenomena.”

The main stumbling block to actually creating a quantum computer has been in minimising the number of resources needed to efficiently implement processing circuits.

“Similar to building a huge wall out lots of small bricks, large quantum circuits require very many logic gates to function. However, if larger bricks are used the same wall could be built with far fewer bricks,” said Dr Patel.

In an experiment involving researchers from Griffith University and the University of Queensland, it was demonstrated how to build larger quantum circuits in a more direct way without using small logic gates.

At present, even small and medium scale quantum computer circuits cannot be produced because of the requirement to integrate so many of these gates into the circuits. One example is the Fredkin (controlled- SWAP) gate. This is a gate where two qubits are swapped depending on the value of the third.

Usually the Fredkin gate requires implementing a circuit of five logic operations. The research team used the quantum entanglement of photons – particles of light – to implement the controlled-SWAP operation directly.

“There are quantum computing algorithms, such as Shor’s algorithm for finding prime factors, that require the controlled-SWAP operation,” said Professor Tim Ralph from the University of Queensland.

The quantum Fredkin gate can also be used to perform a direct comparison of two sets of qubits (quantum bits) to determine whether they are the same or not. This is not only useful in computing but is an essential feature of some secure quantum communication protocols where the goal is to verify that two strings, or digital signatures, are the same.”

Professor Geoff Pryde, from Griffith’s Centre for Quantum Dynamics, is the project’s chief investigator.

“What is exciting about our scheme is that it is not limited to just controlling whether qubits are swapped, but can be applied to a variety of different operations opening up ways to control larger circuits efficiently,” said Professor Pryde.

“This could unleash applications that have so far been out of reach.”

The team is part of the Australian Research Council’s Centre for Quantum Computation and Communication Technology, an effort to exploit Australia’s strong expertise in developing quantum information technologies.

News Release Source : Unlocking the gates to quantum computing

Image Credit : Griffith’s Centre for Quantum Dynamics

Thursday, March 17, 2016

New Discovery Helps to Put Quantum Computers within Closer Reach

New strategy helps quantum bits stay on task

Findings published today in Nature may advance the era of quantum computers.

16 March 2016

National High Magnetic Field Laboratory (MagLab)


MagLab scientists have demonstrated a way to improve the performance of the powerful but persnickety building blocks of quantum computers (called quantum bits, or qubits) by reducing interference from the environment.

[caption id="attachment_757" align="aligncenter" width="665"]New Discovery Helps to Put Quantum Computers within Closer Reach New Discovery Helps to Put Quantum Computers within Closer Reach[/caption]

Published today in the prominent journal Nature, this interdisciplinary collaboration between physicists and chemists may hasten the development of quantum computers.

Quantum computers are one of the holy grails of modern applied physics. Compared to today's computers, which rely on transistors to process "bits" of information in the form of binary 0s or 1s, quantum computers hold the promise of performing certain computational tasks exponentially faster. Their power could potentially dwarf that of today's machines, with huge implications for cryptography, computational chemistry and other fields.

Such astounding feats are possible only in the "quantum" world of atoms and sub-atomic particles, where the physical rules governing how things behave are quite different from those of the "classical" world we live in. But the quantum phenomena that make quantum computers feasible are also the very reason they are extremely challenging to build.

That's the paradoxical nut that a team of scientists, including physicists Dorsa Komijani and Stephen Hill, director of the MagLab's Electron Magnetic Resonance Facility, has spent years attacking. And while they have not broken that nut open entirely, they have made an important crack.

To understand their crack, it helps to first know a few basics about quantum mechanics.

While qubits can take many different forms, the MagLab team worked with carefully designed tungsten oxide molecules that contained a single magnetic holmium ion. The magnetic electrons associated with each holmium ion circulate either clockwise or counterclockwise around the axis of the molecule. These so-called spin states are analogous to the "0s" and "1s" of the computer you may be reading this on. But because we're in the quantum world, there's a bonus: the qubit can be in both the 0 and 1 states at the same time in what is termed a quantum superposition — a kind of heaven for decision-averse wafflers. In this case, the superposition involves a mix of the two spin states, with a spectrum of almost infinite possibilities between the fully clockwise and fully counterclockwise states. This is where the added computational power comes from.

Magnetic qubits can also interact with each other over relatively large distances using their magnetic fields, a phenomenon known as entanglement. In a useful quantum computer, large numbers of entangled qubits would perform in perfect unison. Unfortunately, the real world is full of magnetic disturbances (physicists call this "noise") that can also become entangled with the qubits, interfering with the calculations. It's like being interrupted when you're trying to do complex arithmetic in your head and having to start over. This breakdown is called "decoherence."

In the Nature paper, the MagLab team describes a new way to significantly reduce this decoherence in magnetic molecules.

It turns out that chemists can assemble molecules with special spin states that, when placed in a magnetic field, are immune to magnetic disturbances, similar to the way noise-canceling headphones allow you to listen to your favorite music in high fidelity. This sweet spot that allows qubits to interact without interference is called an atomic clock transition, or ACT. Atomic clocks rely on the same quantum physics principle to remain accurate.

The MagLab team was able to keep its holmium qubit working coherently for 8.4 microseconds — long enough for it to potentially perform useful computational tasks.

"I know 8.4 microseconds doesn't seem like a big deal," said Komijani. "But in molecular magnets, it is a big deal, because it's very, very long. But the important point is not the long coherence time; it's the approach that we used to get to this coherence time."

Now that the MagLab team has shown that ACTs can be used as a mechanism to make quantum computers work, it's up to chemists to tweak more molecules so that they are capable, under the right conditions, of creating a coherence sweet spot for qubits.

"That's why this is important," said Komijani. "We're saying, ‘See, we found this capability in molecular magnets. Now you guys, you chemists, go ahead and make stuff that has this capability so we can find the atomic clock transitions.'"

The Nature paper is part of a larger research effort expected to yield additional publications.

"We're just contributing a tiny, tiny amount of research," said Komijani. "But it's important because it's saying that you can play around with your qubit by changing the magnetic field it's in and moving from where the coherence is very low to the sweet spot, where it's very high."

The other contributors on the Nature paper are Muhandis Shiddiq, a postdoctoral associate in physics at the Technical University in Dortmund, Germany, and former MagLab grad student who is joint first author (with Komijani) on the study; and chemists Yan Duan, Alejandro Gaita-Ariño and Eugenio Coronado, all of the Institute of Molecular Science in Valencia, Spain.

News Release Source : New strategy helps quantum bits stay on task

Image Credit : National High Magnetic Field Laboratory (MagLab)

Thursday, March 10, 2016

The Optical Chip Simultaneously Generate Multiphoton Qubits

INRS takes giant step forward in generating optical qubits

The optical chip developed at INRS by Prof. Roberto Morandotti’s team overcomes a number of obstacles in the development of quantum computers, which are expected to revolutionize information processing. The international research team has demonstrated that on-chip quantum frequency combs can be used to simultaneously generate multiphoton entangled quantum bit (qubit) states.



Quantum computing differs fundamentally from classical computing, in that it is based on the generation and processing of qubits.Unlike classical bits, which can have a state of either 1 or 0, qubits allow a superposition of the 1 and 0 states (both simultaneously).Strikingly, multiple qubits can be linked in so-called ‘entangled’ states, where the manipulation of a single qubit changes the entire system, even if individual qubits are physically distant.This property is the basis for quantum information processing, aiming towards building superfast quantum computers and transferring information in a completely secure way.

[caption id="attachment_751" align="aligncenter" width="640"]The Optical Chip Simultaneously Generate Multiphoton Qubits             The Optical Chip Simultaneously Generate Multiphoton Qubits[/caption]

Professor Morandotti has focused his research efforts on the realization of quantum components compatible with established technologies.The chip developed by his team was designed to meet numerous criteria for its direct use:it is compact, inexpensive to make, compatible with electronic circuits, and uses standard telecommunication frequencies.It is also scalable, an essential characteristic if it is to serve as a basis for practical systems.But the biggest technological challenge is the generation of multiple, stable, and controllable entangled qubit states.

The generation of qubits can rely on several different approaches, includingelectron spins, atomic energy levels, and photon quantum states. Photons have the advantage of preserving entanglement over long distances and time periods.But generating entangled photon states in a compact and scalable way is difficult.“What is most important, several such states have to be generated simultaneously if we are to arrive at practical applications,” added INRS research associate Dr. Michael Kues.

Roberto Morandotti’s team tackled this challenge by using on-chip optical frequency combs for the first time to generate multiple entangled qubit states of light.As Michael Kues explains, optical frequency combs are light sources comprised of many equally-spaced frequency modes.“Frequency combs are extraordinarily precise sources and have already revolutionized metrology and sensing, as well as earning their discoverers the 2005 Nobel Prize in Physics.”

Thanks to these integrated quantum frequency combs, the chip developed by INRS is able to generate entangled multi-photon qubit states over several hundred frequency modes.It is the first time anyone has demonstrated the simultaneous generation of qubit multi-photon and two-photon entangled states:Until now, integrated systems developed by other research teams had only succeeded in generating individual two-photon entangled states on a chip.

The results published in Science will provide a foundation for new research, both in integrated quantum photonics and quantum frequency combs.This could revolutionize optical quantum technologies, while at the same time maintaining compatibility with existing semiconductor chip technology.

News Release Source : INRS takes giant step forward in generating optical qubits

Image Credit : INRS

Thursday, March 3, 2016

Quantum Computers Begin to End The Traditional Encryption Schemes?

The beginning of the end for encryption schemes?

New quantum computer, based on five atoms, factors numbers in a scalable way.

March 3, 2016

What are the prime factors, or multipliers, for the number 15? Most grade school students know the answer — 3 and 5 — by memory. A larger number, such as 91, may take some pen and paper. An even larger number, say with 232 digits, can (and has) taken scientists two years to factor, using hundreds of classical computers operating in parallel.

[caption id="attachment_746" align="aligncenter" width="639"]Quantum Computers Begin to End The Traditional Encryption Schemes?      Quantum Computers Begin to End The Traditional Encryption Schemes?[/caption]

Because factoring large numbers is so devilishly hard, this “factoring problem” is the basis for many encryption schemes for protecting credit cards, state secrets, and other confidential data. It’s thought that a single quantum computer may easily crack this problem, by using hundreds of atoms, essentially in parallel, to quickly factor huge numbers.

In 1994, Peter Shor, the Morss Professor of Applied Mathematics at MIT, came up with a quantum algorithm that calculates the prime factors of a large number, vastly more efficiently than a classical computer. However, the algorithm’s success depends on a computer with a large number of quantum bits. While others have attempted to implement Shor’s algorithm in various quantum systems, none have been able to do so with more than a few quantum bits, in a scalable way.

Now, in a paper published today in the journal Science, researchers from MIT and the University of Innsbruck in Austria report that they have designed and built a quantum computer from five atoms in an ion trap. The computer uses laser pulses to carry out Shor’s algorithm on each atom, to correctly factor the number 15. The system is designed in such a way that more atoms and lasers can be added to build a bigger and faster quantum computer, able to factor much larger numbers. The results, they say, represent the first scalable implementation of Shor’s algorithm.

“We show that Shor’s algorithm, the most complex quantum algorithm known to date, is realizable in a way where, yes, all you have to do is go in the lab, apply more technology, and you should be able to make a bigger quantum computer,” says Isaac Chuang, professor of physics and professor of electrical engineering and computer science at MIT. “It might still cost an enormous amount of money to build — you won’t be building a quantum computer and putting it on your desktop anytime soon — but now it’s much more an engineering effort, and not a basic physics question.”

Seeing through the quantum forest

In classical computing, numbers are represented by either 0s or 1s, and calculations are carried out according to an algorithm’s “instructions,” which manipulate these 0s and 1s to transform an input to an output. In contrast, quantum computing relies on atomic-scale units, or “qubits,” that can be simultaneously 0 and 1 — a state known as a superposition. In this state, a single qubit can essentially carry out two separate streams of calculations in parallel, making computations far more efficient than a classical computer.

In 2001, Chuang, a pioneer in the field of quantum computing, designed a quantum computer based on one molecule that could be held in superposition and manipulated with nuclear magnetic resonance to factor the number 15. The results, which were published in Nature, represented the first experimental realization of Shor’s algorithm. But the system wasn’t scalable; it became more difficult to control the system as more atoms were added.

“Once you had too many atoms, it was like a big forest — it was very hard to control one atom from the next one,” Chuang says. “The difficulty is to implement [the algorithm] in a system that’s sufficiently isolated that it can stay quantum mechanical for long enough that you can actually have a chance to do the whole algorithm.”

“Straightforwardly scalable”

Chuang and his colleagues have now come up with a new, scalable quantum system for factoring numbers efficiently. While it typically takes about 12 qubits to factor the number 15, they found a way to shave the system down to five qubits, each represented by a single atom. Each atom can be held in a superposition of two different energy states simultaneously. The researchers use laser pulses to perform “logic gates,” or components of Shor’s algorithm, on four of the five atoms. The results are then stored, forwarded, extracted, and recycled via the fifth atom, thereby carrying out Shor’s algorithm in parallel, with fewer qubits than is typically required.

The team was able to keep the quantum system stable by holding the atoms in an ion trap, where they removed an electron from each atom, thereby charging it. They then held each atom in place with an electric field.

“That way, we know exactly where that atom is in space,” Chuang explains. “Then we do that with another atom, a few microns away — [a distance] about 100th the width of a human hair. By having a number of these atoms together, they can still interact with each other, because they’re charged. That interaction lets us perform logic gates, which allow us to realize the primitives of the Shor factoring algorithm. The gates we perform can work on any of these kinds of atoms, no matter how large we make the system.”

Chuang’s team first worked out the quantum design in principle. His colleagues at the University of Innsbruck then built an experimental apparatus based on his methodology. They directed the quantum system to factor the number 15 — the smallest number that can meaningfully demonstrate Shor’s algorithm. Without any prior knowledge of the answers, the system returned the correct factors, with a confidence exceeding 99 percent.

“In future generations, we foresee it being straightforwardly scalable, once the apparatus can trap more atoms and more laser beams can control the pulses,” Chuang says. “We see no physical reason why that is not going to be in the cards.”

Mark Ritter, senior manager of physical sciences at IBM, says the group’s method of recycling qubits reduces the resources required in the system by a factor of 3 — a significant though small step towards scaling up quantum computing.

“Improving the state-of-the-art by a factor of 3 is good,” says Ritter. But truly scaling the system “requires orders of magnitude more qubits, and these qubits must be shuttled around advanced traps with many thousands of simultaneous laser control pulses.”

If the team can successfully add more quantum components to the system, Ritter says it will have accomplished a long-unrealized feat.

“Shor's algorithm was the first non-trivial quantum algorithm showing a potential of ‘exponential’ speed-up over classical algorithms,” Ritter says. “It captured the imagination of many researchers who took notice of quantum computing because of its promise of truly remarkable algorithmic acceleration. Therefore, to implement Shor's algorithm is comparable to the ‘Hello, World’ of classical computing.”

What will all this eventually mean for encryption schemes of the future?

“Well, one thing is that if you are a nation state, you probably don’t want to publicly store your secrets using encryption that relies on factoring as a hard-to-invert problem,” Chuang says. “Because when these quantum computers start coming out, you’ll be able to go back and unencrypt all those old secrets.”

News Source Release : The beginning of the end for encryption schemes?