Quantum Internet Update: Quantum entanglement works through 50 km of optical fiber

One could envisage building the world’s first intercity light-matter quantum network in the coming years. (Credit: IQOQI Innsbruck/Harald Ritsch)

For the first time, a team led by Innsbruck physicist Ben Lanyon has sent a light particle entangled with matter over 50 km of optical fiber. This paves the way for the practical use of quantum networks and sets a milestone for a future quantum internet.

The quantum internet promises absolutely tap-proof communication and powerful distributed sensor networks for new science and technology. However, because quantum information cannot be copied, it is not possible to send this information over a classical network. Quantum information must be transmitted by quantum particles, and special interfaces are required for this. The Innsbruck-based experimental physicist Ben Lanyon, who was awarded the Austrian START Prize in 2015 for his research, is researching these important intersections of a future quantum Internet. Now his team at the Department of Experimental Physics at the University of Innsbruck and at the Institute of Quantum Optics and Quantum Information of the Austrian Academy of Sciences has achieved a record for the transfer of quantum entanglement between matter and light. For the first time, a distance of 50 kilometers was covered using fiber optic cables. “This is two orders of magnitude further than was previously possible and is a practical distance to start building inter-city quantum networks,” says Ben Lanyon.

Converted photon for transmission

Lanyon’s team started the experiment with a calcium atom trapped in an ion trap. Using laser beams, the researchers write a quantum state onto the ion and simultaneously excite it to emit a photon in which quantum information is stored. As a result, the quantum states of the atom and the light particle are entangled. But the challenge is to transmit the photon over fiber optic cables. “The photon emitted by the calcium ion has a wavelength of 854 nanometers and is quickly absorbed by the optical fiber”, says Ben Lanyon. His team therefore initially sends the light particle through a nonlinear crystal illuminated by a strong laser. Thereby the photon wavelength is converted to the optimal value for long-distance travel: the current telecommunications standard wavelength of 1550 nanometers. The researchers from Innsbruck then send this photon through a 50-kilometer-long optical fiber line. Their measurements show that atom and light particle are still entangled even after the wavelength conversion and this long journey.

Even greater distances in sight

As a next step, Lanyon and his team show that their methods would enable entanglement to be generated between ions 100 kilometers apart and more. Two nodes send each an entangled photon over a distance of 50 kilometers to an intersection where the light particles are measured in such a way that they lose their entanglement with the ions, which in turn would entangle them. With 100-kilometer node spacing now a possibility, one could therefore envisage building the world’s first intercity light-matter quantum network in the coming years: only a handful of trapped ion-systems would be required on the way to establish a quantum internet between Innsbruck and Vienna, for example.

Learn more: Entan­gle­ment sent over 50 km of opti­cal fiber

 

The Latest on: Quantum internet

via  Bing News

 

One more step to a super-secure quantum internet

via MIT Review

Scientists have managed to send a record-breaking amount of data in quantum form, using a strange unit of quantum information called a qutrit.

The news: Quantum tech promises to allow data to be sent securely over long distances. Scientists have already shown it’s possible to transmit information both on land and via satellites using quantum bits, or qubits. Now physicists at the University of Science and Technology of China and the University of Vienna in Austria have found a way to ship even more data using something called quantum trits, or qutrits.

Qutrits? Oh, come on, you’ve just made that up: Nope, they’re real. Conventional bits used to encode everything from financial records to YouTube videos are streams of electrical or photonic pulses than can represent either a or a 0. Qubits, which are typically electrons or photons, can carry more information because they can be polarized in two directions at once, so they can represent both a and a at the same time. Qutrits, which can be polarized in three different dimensions simultaneously, can carry even more information. In theory, this can then be transmitted using quantum teleportation.
Quantum … what? Quantum teleportation is a method for shipping data that relies on an almost-mystical phenomenon called entanglement. Entangled quantum particles can influence one another’s state, even if they are continents apart. In teleportation, a sender and receiver each receive one of a pair of entangled qubits. The sender measures the interaction of their qubit with another one that holds data they want to send. By applying the results of this measurement to the other entangled qubit, the receiver can work out what information has been transmitted. (For a more detailed look at quantum teleportation, see our explainer here.)

Measuring progress: Getting this to work with qubits isn’t easy—and harnessing qutrits is even harder because of that extra dimension. But the researchers, who include Jian-Wei Pan, a Chinese pioneer of quantum communication, say they have cracked the problem by tweaking the first part of the teleportation process so that senders have more measurement information to pass on to receivers. This will make it easier for the latter to work out what data has been teleported over. The research was published in the journal Physical Review Letters.

Deterring hackers: This might seem rather esoteric, but it has huge implications for cybersecurity. Hackers can snoop on conventional bits flowing across the internet without leaving a trace. But interfering with quantum units of information causes them to lose their delicate quantum state, leaving a telltale sign of hacking. If qutrits can be harnessed at scale, they could form the backbone of an ultra-secure quantum internet that could be used to send highly sensitive government and commercial data.

Learn more: A super-secure quantum internet just took another step closer to reality

 

The Latest on: Quantum internet

via  Bing News

 

A major step towards a quantum internet

Figure. Schematic image of the spin detection of a circularly polarized photon exciting an electron spin. The yellow nano-fabricated metal electrodes form the pockets required to trap the electrons, move them, and sense them.

A research team led by Osaka University demonstrated how information encoded in the circular polarization of a laser beam can be translated into the spin state of an electron in a quantum dot, each being a quantum bit and a quantum computer candidate. The achievement represents a major step towards a “quantum internet,” in which future computers can rapidly and securely send and receive quantum information.

Quantum computers have the potential to vastly outperform current systems because they work in a fundamentally different way. Instead of processing discrete ones and zeros, quantum information, whether stored in electron spins or transmitted by laser photons, can be in a superposition of multiple states simultaneously. Moreover, the states of two or more objects can become entangled, so that the status of one cannot be completely described without this other. Handling entangled states allow quantum computers to evaluate many possibilities simultaneously, as well as transmit information from place to place immune from eavesdropping.

However, these entangled states can be very fragile, lasting only microseconds before losing coherence. To realize the goal of a quantum internet, over which coherent light signals can relay quantum information, these signals must be able to interact with electron spins inside distant computers.

Researchers led by Osaka University used laser light to send quantum information to a quantum dot by altering the spin state of a single electron trapped there. While electrons don’t spin in the usual sense, they do have angular momentum, which can be flipped when absorbing circularly polarized laser light.

“Importantly, this action allowed us to read the state of the electron after applying the laser light to confirm that it was in the correct spin state,” says first author Takafumi Fujita. “Our readout method used the Pauli exclusion principle, which prohibits two electrons from occupying the exact same state. On the tiny quantum dot, there is only enough space for the electron to pass the so-called Pauli spin blockade if it has the correct spin.”

Quantum information transfer has already been used for cryptographic purposes. “The transfer of superposition states or entangled states allows for completely secure quantum key distribution,” senior author Akira Oiwa says. “This is because any attempt to intercept the signal automatically destroys the superposition, making it impossible to listen in without being detected.”

The rapid optical manipulation of individual spins is a promising method for producing a quantum nano-scale general computing platform. An exciting possibility is that future computers may be able to leverage this method for many other applications, including optimization and chemical simulations.

Learn more: Travelling towards a quantum internet at light speed

 

The Latest on: Quantum internet

via  Bing News

 

A device that could serve as the backbone of a future quantum Internet

Professor Hoi-Kwong Lo (ECE) and his collaborators have performed a proof-of-principle experiment on a key aspect of all-photonic quantum repeaters (Photo: Jessica MacInnis)

U of T Engineering researchers have demonstrated proof-of-principle for a device that could serve as the backbone of a future quantum Internet. Professor Hoi-Kwong Lo (ECE, Physics) and his collaborators have developed a prototype for a key element for all-photonic quantum repeaters, a critical step in long-distance quantum communication.

A quantum Internet is the ‘Holy Grail’ of quantum information processing, enabling many novel applications including information-theoretic secure communication. Today’s Internet was not specifically designed for security, and it shows: hacking, break-ins and computer espionage are common challenges. Nefarious hackers are constantly poking holes in sophisticated layers of defence erected by individuals, corporations and governments.

In light of this, researchers have proposed other ways of transmitting data that would leverage key features of quantum physics to provide virtually unbreakable encryption. One of the most promising technologies involves a technique known as quantum key distribution (QKD). QKD exploits the fact that the simple act of sensing or measuring the state of a quantum system disturbs that system. Because of this, any third-party eavesdropping would leave behind a clearly detectable trace, and the communication can be aborted before any sensitive information is lost.

Until now, this type of quantum security has been demonstrated in small-scale systems. Lo and his team are among a group of researchers around the world who are laying the groundwork for a future quantum Internet by working to address some of the challenges in transmitting quantum information over great distances, using optical fibre communication.

Because light signals lose potency as they travel long distances through fibre-optic cables, devices called repeaters are inserted at regular intervals along the line. These repeaters boost and amplify the signals to help transmit the information along the line.

But quantum information is different, and existing repeaters for quantum information are highly problematic. They require storage of the quantum state at the repeater sites, making the repeaters much more error prone, difficult to build, and very expensive because they often operate at cryogenic temperatures.

Lo and his team have proposed a different approach. They are working on the development of the next generation of repeaters, called all-photonic quantum repeaters, that would eliminate or reduce many of the shortcomings of standard quantum repeaters. With collaborators at Osaka University, Toyama University and NTT Corporation in Japan, Lo and his team have demonstrated proof-of-concept of their work in a paper recently published in Nature Communications.

“We have developed all-photonic repeaters that allow time-reversed adaptive Bell measurement,” says Lo. “Because these repeaters are all-optical, they offer advantages that traditional — quantum-memory-based matter — repeaters do not. For example, this method could work at room temperature.”

A quantum Internet could offer applications that are impossible to implement in the conventional Internet, such as impenetrable security and quantum teleportation.

“An all-optical network is a promising form of infrastructure for fast and energy-efficient communication that is required for a future quantum internet,” says Lo. “Our work helps pave the way toward this future.”

Learn more: Toward a future quantum Internet

 

 

The Latest on: Quantum internet

via  Bing News

 

 

A new building block falls in place for quantum computing

The team’s quantum frequency processor operates on photons (spheres) through quantum gates (boxes), synonymous with classical circuits for quantum computing. Superpositions are shown by spheres straddling multiple lines; entanglements are visualized as clouds. Credit: Andy Sproles/Oak Ridge National Laboratory, U.S. Department of Energy

Researchers with the Department of Energy’s Oak Ridge National Laboratory have demonstrated a new level of control over photons encoded with quantum information. Their research was published in Optica.

Joseph Lukens, Brian Williams, Nicholas Peters, and Pavel Lougovski, research scientists with ORNL’s Quantum Information Science Group, performed distinct, independent operations simultaneously on two qubits encoded on photons of different frequencies, a key capability in linear optical quantum computing. Qubits are the smallest unit of quantum information.

Quantum scientists working with frequency-encoded qubits have been able to perform a single operation on two qubits in parallel, but that falls short for quantum computing.

“To realize universal quantum computing, you need to be able to do different operations on different qubits at the same time, and that’s what we’ve done here,” Lougovski said.

According to Lougovski, the team’s experimental system—two entangled photons contained in a single strand of fiber-optic cable—is the “smallest quantum computer you can imagine. This paper marks the first demonstration of our frequency-based approach to universal quantum computing.”

“A lot of researchers are talking about quantum information processing with photons, and even using frequency,” said Lukens. “But no one had thought about sending multiple photons through the same fiber-optic strand, in the same space, and operating on them differently.”

The team’s quantum frequency processor allowed them to manipulate the frequency of photons to bring about superposition, a state that enables quantum operations and computing.

Unlike data bits encoded for classical computing, superposed qubits encoded in a photon’s frequency have a value of 0 and 1, rather than 0 or 1. This capability allows quantum computers to concurrently perform operations on larger datasets than today’s supercomputers.

Using their processor, the researchers demonstrated 97 percent interference visibility—a measure of how alike two photons are—compared with the 70 percent visibility rate returned in similar research. Their result indicated that the photons’ quantum states were virtually identical.

The researchers also applied a statistical method associated with machine learning to prove that the operations were done with very high fidelity and in a completely controlled fashion.

“We were able to extract more information about the quantum state of our experimental system using Bayesian inference than if we had used more common statistical methods,” Williams said.

“This work represents the first time our team’s process has returned an actual quantum outcome.”

Williams pointed out that their experimental setup provides stability and control. “When the photons are taking different paths in the equipment, they experience different phase changes, and that leads to instability,” he said. “When they are traveling through the same device, in this case, the fiber-optic strand, you have better control.”

Stability and control enable quantum operations that preserve information, reduce information processing time, and improve energy efficiency. The researchers compared their ongoing projects, begun in 2016, to building blocks that will link together to make large-scale quantum computing possible.

“There are steps you have to take before you take the next, more complicated step,” Peters said. “Our previous projects focused on developing fundamental capabilities and enable us to now work in the fully quantum domain with fully quantum input states.”

Lukens said the team’s results show that “we can control qubits’ quantum states, change their correlations, and modify them using standard telecommunications technology in ways that are applicable to advancing quantum computing.”

Once the building blocks of quantum computers are all in place, he added, “we can start connecting quantum devices to build the quantum internet, which is the next, exciting step.”

Much the way that information is processed differently from supercomputer to supercomputer, reflecting different developers and workflow priorities, quantum devices will function using different frequencies. This will make it challenging to connect them so they can work together the way today’s computers interact on the internet.

This work is an extension of the team’s previous demonstrations of quantum information processing capabilities on standard telecommunications technology. Furthermore, they said, leveraging existing fiber-optic network infrastructure for quantum computing is practical: billions of dollars have been invested, and quantum information processing represents a novel use.

The researchers said this “full circle” aspect of their work is highly satisfying. “We started our research together wanting to explore the use of standard telecommunications technology for quantum information processing, and we have found out that we can go back to the classical domain and improve it,” Lukens said.

Learn more: Researchers demonstrate new building block in quantum computing

 

 

The Latest on: Quantum computing
  • IBM Quantum Computer to Help Develop Next-gen Lithium Sulfur Batteries
    on January 13, 2020 at 2:53 pm

    He fundraises for various high impact technology companies and has worked in computer technology, insurance, healthcare and with corporate finance. He has substantial familiarity with a broad range of ...

  • More quantum funding coming from DOE
    on January 13, 2020 at 12:34 pm

    Individual awards are planned in the range of $10 million to $25 million per year over the five-year span. The legislation, signed into law in January 2019, launched a 10-year plan to accelerate ...

  • DOE launches quantum funding opportunity
    on January 13, 2020 at 12:19 pm

    Individual awards are planned in the range of $10 million to $25 million per year over the five-year span. The legislation, signed into law in January 2019, launched a 10-year plan to accelerate ...

  • IBM doubles quantum volume in the race for computing supremacy
    on January 13, 2020 at 11:04 am

    Jamie Garcia, global lead for Quantum Applications, IBM Research, talks at CES 2020 about how IBM reached milestones in quantum computing in 2019. Teena Maddox: Hi, I'm here at CES 2020 talking to Dr.

  • Influential electrons? Physicists uncover a quantum relationship
    on January 13, 2020 at 8:05 am

    A team of physicists has mapped how electron energies vary from region to region in a particular quantum state with unprecedented clarity. This understanding reveals an underlying mechanism by which ...

  • Los Alamos joins IBM quantum computing network
    on January 13, 2020 at 5:59 am

    Los Alamos National Laboratory is joining the IBM Q Network. Researchers will have access to 15 universal quantum computing systems, including a 53 quantum bits (qubit) system. The lab says, by ...

  • CES 2020: IBM's quantum computing milestones
    on January 13, 2020 at 5:59 am

    Tonya Hall sits down with Dr. Jeff Welser, vice president of IBM Research Almaden, pacific rim labs, and global exploratory science, to learn more about how IBM has achieved the highest quantum volume ...

  • Delta Air Lines becomes first company to join IBM’s quantum computing hub at NC State
    on January 11, 2020 at 6:00 am

    A little more than a year and a half after IBM launched a quantum computing hub on N.C. State University’s Centennial Campus, Delta Air Lines will be the first industry partner to work there. It’s the ...

  • 2020s are the decade of commercial quantum computing, says IBM
    on January 10, 2020 at 3:58 am

    There's plenty of uncertainty to go around in the quantum-computing world, from the weird behaviour of the qubits themselves right up to which tech companies are going to come out on top. IBM took the ...

via  Bing News