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Researchers develop new chip to bridge the gap between quantum and classical computing

The Gap between quantum and classical computing is bridged by this new chip

Quantum computers existing today are limited versions of the futuristic quantum computers that we hope to achieve in the future. However, scientists have created the hardware for the “probabilistic computer” – a device to bridge the gap between the standard PCs of today and the genuine quantum computers. The study appears in the Nature journal. 

This probabilistic computer can solve quantum problems using a special trick. It uses a p-bit which is described by the research team as “poor man’s qubit”. In classical computing, a bit can either take the value 1 or 0, while qubits can take both of these values at the same time as per the laws of quantum computing. Meanwhile, the p-bit can take only 1 or 0 at a time, but the switch between two states occurs very quickly. Using the fluctuations properly, researchers can tackle the problems that are considered quantum computing problems without using a real quantum computer. 

In addition to this, the p-bit can operate at room temperature whereas the qubits need super-cold conditions for their operation. P-bits can be easily adapted to the existing computers. Supriyo Datta, an electrical engineer at Purdue University, in Indiana, said that there are a group of problems solved with the help of qubits that can also be solved by the p-bits. Hence getting the name “poor man’s qubit”. 

The result of the research has been a modified magnetoresistive random access memory(MRAM) device for storing information in the computers of the present day. Magnetic orientations are used to represent 0s or 1s using states of resistance. Eight custom-made MRAM p-bit units were put with a controller chip to create a probabilistic computer – where units are used to take a specific value. 

Scientists were able to solve the integer factorization problems, which are usually considered quantum problems. It can also be solved by classical computers however with lesser efficiency. The probabilistic computer along with p-bits represents a middle ground between two ends. Scientists feel that the fully developed p-bit computers would solve integer factorization problems with lesser energy and time than the computers of the present day. 

Ahmed Zeeshan Pervaiz, Purdue University said that the circuit occupies the same area as that of a transistor but performs the function which would take several thousand transistors to perform. The calculation speed could also be increased by parallel operation of a huge number of p-bits. 

For the practical use of these machines, there is a need for more refining which would not take much time. After that, these can handle certain problems until the final leap in quantum computing occurs. Connecting qubits for practical use is a tough challenge until then p-bits can be used for machine learning and optimization problems. 

Journal Reference: Nature

qubit

Researchers for the first time report quantum teleportation in qutrit

Scientists have successfully completed teleportation of a qutrit which is a piece of quantum information based on three states and this has opened a whole new host of opportunities and possibilities for quantum computing and communication sector.

Until now, Qubits were used for quantum transportation for long distances, however, a new proof of concept study has shown that future quantum networks will be able to carry much more data with lesser interference that was being thought. Bits in classical computing can be in two states, either 1 or 0. However, in quantum computing, there is qubit which can be both 0 or 1 at the same time called superposition. Qutrit has a similar relation to a trit, adding superposition to the classical examples, that are represented as 0,1 or 2. A qutrit can be all of these at one single time, which makes a huge leap in terms of computer processing power or the amount of information that can be sent at once. It adds another level of complexity for quantum computing researchers.

Quantum teleportation is simply getting the quantum information from one place to the other through a process called quantum entanglement. It is a case when two quantum particles are interlinked and one reveals the properties of the other, no matter how far apart they might be present. The quantum information can be beamed via photons of light that might be used in the future to create an unhackable internet network which will be protected by fundamental laws of physics.

By splitting the path of a photon into 3 parts close to each other in a careful manner with lasers, beam splitters and barium crystals, researchers were able to create qutrit and generate entanglement.

The system produced a fidelity of 0.75 over a measurement of 12 states which is an accurate result. The setup remained slow and inefficient but has shown that quantum teleportation is possible. Daniel Garisto reports in Scientific American, that another group of scientists have recorded teleportation across 10 states but their work has not yet been accepted by a peer-reviewed journal. They would also upgrade their systems in the future maybe even to the heights of ququarts.

Researchers mentioned that their work provides a complete toolbox for teleporting a particle in an intact manner by combining previous methods of teleportation of two-particle systems and multiple degrees of freedom. The scientists expect their results will pave way for quantum technology applications in higher dimensions since teleportation plays a central role in quantum networks and repeaters.

Journal Reference: arxiv

Quantum Computing Ion Trapping

Neven’s law to possibly replace Moore’s law for quantum computing processors

New disruptive technology is promising to take the power of computing to unprecedented heights. And for predicting the speed of the progress of “quantum computing” technology, Hartmut Neven, director of Quantum AI Labs of Google has given the proposal of a new rule for quantum computers that is similar to Moore’s Law which measured the progress of normal computers for more than 50 years. But the question is if “Neven’s Law” can be trusted as an actual representation of what is occurring in quantum computing and what will be the situation in the future. 

Quantum computers use physical systems for storing data unlike the normal computers which store data as electrical signals having either of 0 or 1 state. This helps in encoding information in multiple states that allows exponentially faster calculations than the normal computers. It is still in infancy and a quantum computer has not been built yet which crosses the existing supercomputers. There is some skepticism about its progress however there is also excitement now how quick the progress is occurring. Thus it would be helpful to have an idea of what can be expected from quantum computers in future. 

Moore’s law describes that the processing power of normal digital computers to double almost every two years creating exponential growth. It is named after Gordon Moore, Intel co-founder and it accurately describes the rate of increase in the transistor number which can be integrated into a silicon microchip. Moore’s law is not applicable to quantum computers as they are designed differently on basis of laws of quantum physics. This is where Neven’s law states that quantum computing power is experiencing doubly exponential growth relative to normal computing.

Doubly exponential growth increases in powers of powers of two: 2^2 (4), 2^4 (16), 2^8 (256), 2^16 (65,536) and so on. If this was applicable to normal computers in Moore’s law, then smartphones and computers would have been present by 1975. Neven hopes that this fast pace should lead to quantum advantage where the smaller quantum processors overtake the highly powerful supercomputers. 

Neven said that researchers at Google can decrease the error rate in the prototypes of quantum computers, allowing them to build more complex and powerful machines with every iteration. This progress is exponential however a quantum processor is exponentially better than a normal processor of the same size. Reason being a quantum effect called entanglement allows various computational tasks to be performed at the same time creating exponential rates. Hence, quantum processors developing at an exponential rate and being exponentially faster than normal processors makes them develop at a doubly exponential rate than the classical processors. 

Although this is exciting, the Neven’s rule is based on a small number of prototypes where progress has been measured in a small period of time. So several data points can be taken which fits other growth patterns. There is also the issue that as quantum processors become more powerful, the small technical problems get much larger. The minor electrical noise in quantum computers leading to errors could grow in frequency as the complexity of the processor grows. This could be solved by using error correction protocols, where many backup hardwares have to be added to the redundant processor. Hence the computer would have to be much more complex without gaining any extra power. This could impact Neven’s rule.

Moore’s law foresaw the progress of normal computing for a time period of 50 years without being a fundamental natural law. It allowed the microchip industry to adopt roadmaps for developing regular milestones, assess investment and evaluate revenues. If Neven’s rule becomes as prophetic as Moore’s law it will have ramifications more than the prediction of quantum computing performance. We do not know yet about the commercialisation of quantum computers, however, this can be quickly known if Neven’s law holds true. 

Schrodinger cat in box

Researchers can predict the jumps of Schrodinger’s cat and save it

Researchers from Yale University have found out a way to catch and save the famous Schrodinger’s cat, by anticipating its moves beforehand and taking necessary actions to save it from its doom. Schrodinger’s cat is the symbol of quantum unpredictability that was designed by Austrian scientist, Erwin Schrödinger in the year 1935. During this entire process, scientists have managed to discard several years of dogma which was present in quantum physics.

Through this discovery, researchers can set up early warning systems for the imminent jumps made by artificial atoms which contain quantum data. The study was published in the Nature journal.

Schrodinger’s cat is a famous paradox which is designed for illustrating the superposition concept. It is the ability of two states which are unpredictable in nature to exist simultaneously. It goes like this, a cat is trapped in a box which is closed tightly. It contains a radioactive source and a poison will be triggered with the decay of a radioactive atom. With the help of quantum physics’ superposition theory we know that the cat will be both alive and dead until the box is opened by someone. By opening the box and thus making an observation, a random change in the quantum state of the cat occurs and it is either living or is dead.

The experiment which has been conducted in the laboratory of Yale professor, Michel Devoret and proposed by Zlatko Minev, the principal author studies for the first time what actually happens in a quantum jump. The results have surprisingly contradicted the view of renowned Danish physicist, Niels Bohr. 

When microscopic entities such as electrons, atoms or artificial atoms having quantum information makes a quantum jump, the transition is sudden. It occurs from one discrete state to another. These jumps were theorized by Niels Bohr about a century ago but they were observed for the first time in atoms in 1980s.

In the experiment, researchers used three microwave generators for monitoring the atom which was enclosed in a 3D aluminium cavity. It allowed the researchers to observe the atom with a very high efficiency. The microwave radiations stir the atom, which makes a jump. The quantum signal of the jump can be amplified without disturbing the room temperature. It helped the scientists to observe a sudden absence of the detection photons which are emitted by the ancillary atomic state, excited by the microwaves. This gave the warning of the jump.

Minev noted the similarity of the jump with that of the volcanic eruption. Both are unpredictable but with correct warning, the advance disaster can be detected and acted on.

Quantum network

Establishing the ultimate limits of quantum communication networks

At the moment, sensitive data is typically encrypted and then sent across fibre-optic cables and other channels together with the digital “keys” needed to decode the information. However, the data can be vulnerable to hackers.

Quantum communication takes advantage of the laws of quantum physics to protect data. These laws allow particles—typically photons of light —to transmit the data using quantum bits, or qubits.

Superior capabilities

Multinational corporations, such as IBM and Google, are now building intermediate-size quantum computers with increasing number of quantum units or qubits.

Once they scaled up to larger sizes, these devices will have far-superior capabilities than current classical computers. For instance, they may process extremely large numbers in just a few seconds, speed-up many fundamental mathematical operations, and perfectly simulate molecular and biological processes.

One challenge will be to connect quantum computers together, in order to create a quantum-version of the Internet or " quantum Internet".

However, an important but unanswered question remains: what is the ultimate rate at which one can transmit secret messages or quantum systems from one remote quantum computer to another?

Notoriously difficult

Writing in the journal Communications PhysicsProfessor Stefano Pirandola, from the University of York’s Department of Computer Science, said scientists have answered the question.

Prof Pirandola studied the optimal working mechanism of a future quantum Internet, and also provided the ultimate secret-key capacities that can potentially be achieved.

He said: “Studying quantum networks is notoriously difficult, but recent mathematical tools developed in quantum information theory have allowed us to completely simplify the analysis.

Qubits

“An outstanding question was to compute the maximum number of elementary quantum systems (known as qubits) that could be reliably transmitted from one user of the network to another, or similarly, the maximum number of completely secret bits that these remote users could share.

“This number has now a precise analytical formula.”

Furthermore, the study reveals that the classical-inspired strategy of simultaneously sending qubits through multiple routes of the network can remarkably boost the rate, i.e., the speed of the quantum communication between any two remote users.

Materials required University of York