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Category: quantum physics – Page 673

Efficient Quantum-Mechanical Interface Leads to a Strong Interaction Between Light and Matter

Circa 2020 o.o!

Researchers have succeeded in creating an efficient quantum-mechanical light-matter interface using a microscopic cavity. Within this cavity, a single photon is emitted and absorbed up to 10 times by an artificial atom. This opens up new prospects for quantum technology, report physicists at the University of Basel and Ruhr-University Bochum in the journal Nature.

Quantum physics describes photons as light particles. Achieving an interaction between a single photon and a single atom is a huge challenge due to the tiny size of the atom. However, sending the photon past the atom several times by means of mirrors significantly increases the probability of an interaction.

In order to generate photons, the researchers use artificial atoms, known as quantum dots. These semiconductor structures consist of an accumulation of tens of thousands of atoms, but behave much like a single atom: when they are optically excited, their energy state changes and they emit a photon. “However, they have the technological advantage that they can be embedded in a semiconductor chip,” says Dr. Daniel Najer, who conducted the experiment at the Department of Physics at the University of Basel.

Physicists Harnessed Thousands of Molecules Into a Single Quantum State

In a major milestone for quantum physics, thousands of molecules have been induced to share the same quantum state, dancing together in unison like one huge super molecule.

This is a goal long-sought by physicists, who hope to harness complex quantum systems for technological applications — but getting a bunch of unruly molecules to work together is on a difficulty par with herding cats.

“People have been trying to do this for decades, so we’re very excited,” said physicist Cheng Chin from the University of Chicago.

Nvidia Entangled in Quantum Simulators

Quantum simulators are a strange breed of systems for purposes that might seem a bit nebulous from the outset. These are often HPC clusters with fast interconnects and powerful server processors (although not usually equipped with accelerators) that run a literal simulation of how various quantum circuits function for design and testing of quantum hardware and algorithms. Quantum simulators do more than just test. They can also be used to emulate quantum problem solving and serve as a novel approach to tackling problems without all the quantum hardware complexity.

Despite the various uses, there’s only so much commercial demand for quantum simulators. Companies like IBM have their own internally and for others, Atos/Bull have created these based on their big memory Sequanna systems but these are, as one might imagine, niche machines for special purposes. Nonetheless, Nvidia sees enough opportunity in this arena to make an announcement at their GTC event about the performance of quantum simulators using the DGX A100 and its own custom-cooked quantum development software stack, called CuQuantum.

After all, it is probably important for Nvidia to have some kind of stake in quantum before (and if) it ever really takes off, especially in large-scale and scientific computing. What better way to get an insider view than to work with quantum hardware and software developers who are designing better codes and qubits via a benchmark and testing environment?

Google performed the first quantum simulation of a chemical reaction

Circa 2020 o.,.o!

By Leah Crane.

Google researchers have used a quantum computer to simulate a chemical reaction for the first time. The reaction is a simple one, but this marks a step towards finding a practical use for quantum computers.

Because atoms and molecules are systems governed by quantum mechanics, quantum computers are expected to be the best way to precisely simulate them. These computers use quantum bits, or qubits, to store information and perform calculations. However, quantum computers have difficulty achieving the precision needed to simulate large atoms or chemical reactions.

Decoding Quantum Errors Using Subspace Expansions

O,.o circa 2020.

With the rapid developments in quantum hardware comes a push towards the first practical applications on these devices. While fully fault-tolerant quantum computers may still be years away, one may ask if there exist intermediate forms of error correction or mitigation that might enable practical applications before then. In this work, we consider the idea of post-processing error decoders using existing quantum codes, which are capable of mitigating errors on encoded logical qubits using classical post-processing with no complicated syndrome measurements or additional qubits beyond those used for the logical qubits. This greatly simplifies the experimental exploration of quantum codes on near-term devices, removing the need for locality of syndromes or fast feed-forward, allowing one to study performance aspects of codes on real devices. We provide a general construction equipped with a simple stochastic sampling scheme that does not depend explicitly on a number of terms that we extend to approximate projectors within a subspace. This theory then allows one to generalize to the correction of some logical errors in the code space, correction of some physical unencoded Hamiltonians without engineered symmetries, and corrections derived from approximate symmetries. In this work, we develop the theory of the method and demonstrate it on a simple example with the perfect [[5, 1, 3]] code, which exhibits a pseudo-threshold of p≈0.50 under a single qubit depolarizing channel applied to all qubits. We also provide a demonstration under the application of a logical operation and performance on an unencoded hydrogen molecule, which exhibits a significant improvement over the entire range of possible errors incurred under a depolarizing channel.

Researchers realize high-efficiency frequency conversion on integrated photonic chip

A team led by Prof. GUO Guangcan and Prof. ZOU Changling from the University of Science and Technology of China of the Chinese Academy of Sciences realized efficient frequency conversion in microresonators via a degenerate sum-frequency process, and achieved cross-band frequency conversion and amplification of converted signal through observing the cascaded nonlinear optical effects inside the microresonator. The study was published in Physical Review Letters.

Coherent frequency process has wide application in classical and quantum information fields such as communication, detection, sensing, and imaging. As a bridge connecting wavebands between fiber telecommunications and atomic transition, coherent frequency conversion is a necessary interface for distributed quantum computing and quantum networks.

Integrated nonlinear photonic chip stands out because of its significant technological advances of improving by microresonator’s enhancing the light-matter interaction, along with other advantages like small size, great scalability, and low energy consumption. These make integrated nonlinear photonic chips an important platform to covert optical frequency efficiently and realize other nonlinear optical effects.

Cambridge Quantum pushes into NLP and quantum computing with new head of AI

Cambridge Quantum Computing (CQC) hiring Stephen Clark as head of AI last week could be a sign the company is boosting research into ways quantum computing could be used for natural language processing.

Quantum computing is still in its infancy but promises such significant results that dozens of companies are pursuing new quantum architectures. Researchers at technology giants such as IBM, Google, and Honeywell are making measured progress on demonstrating quantum supremacy for narrowly defined problems. Quantum computers with 50–100 qubits may be able to perform tasks that surpass the capabilities of today’s classical digital computers, “but noise in quantum gates will limit the size of quantum circuits that can be executed reliably,” California Institute of Technology theoretical physics professor John Preskill wrote in a recent paper. “We may feel confident that quantum technology will have a substantial impact on society in the decades ahead, but we cannot be nearly so confident about the commercial potential of quantum technology in the near term, say the next 5 to 10 years.”

CQC has been selling software focused on specific use cases, such as in cybersecurity and pharmaceutical and drug delivery, as the hardware becomes available. “We are very different from the other quantum software companies that we are aware of, which are primarily focused on consulting-based revenues,” CQC CEO Ilyas Khan told VentureBeat.

SeeDevice’s QUANTUM IMAGE SENSOR may be the first to appear on the market, and will allow better low-light imaging than the Sionyx “black silicone” color night-vision cameras

This year-old zdnet article notes that the company plans a photo-sensitivi ty range from ultraviolet through visible light to 2000nm infrared. The sensor itself retains almost 4x the light of ordinary CMOS sensors, while being 2000x more sensitive to light. This will put it on par with the best analogue image intensification tubes used for night vision. Up until now, there have not been any digital night vision systems that can match analogue systems. This will be better, with higher resolution and multichromatic. It also has a 100x greater dynamic range than ordinary CMOS sensors, according to the specifications from SeeDevice’s site linked below. (This means that it can image both bright and dark areas clearly and simultaneously, instead of having the bright areas washing out the image, or the dark areas being black. The included photo is from its website, demonstrating a wide dynamic range photo produced by the system. On a normal photo, either the sky would appear black, or the road would be so bright that it would look washed out.)

Hopefully coming soon to a cell phone camera near you…

SeeDevice’s site: https://www.seedeviceinc.com/technology

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