Quantum Computer, How Does It Work And What It Can Do?

Quantum computers perform calculations based on the probability of an object's state before it is measured - instead of just 1s or 0s - which means they have the potential to process exponentially more data compared to classical computers.

Classical computers carry out logical operations using the definite position of a physical state. These are usually binary, meaning its operations are based on one of two positions. A single state - such as on or off, up or down, 1 or 0 - is called a bit.

In quantum computing, operations instead use the quantum state of an object to produce what's known as a qubit. These states are the undefined properties of an object before they have been detected, such as the spin of an electron or the polarization of a photon.

Rather than having a clear position, unmeasured quantum states occur in a mixed 'superposition', not unlike a coin spinning through the air before it lands in your hand. These superpositions can be entangled with those of other objects, meaning their final outcomes will be mathematically related even if we don't know yet what they are.

The complex mathematics behind these unsettled states of entangled 'spinning coins' can be plugged into special algorithms to make short work of problems that would take a classical computer a long time to work out. Such algorithms would be useful in solving particular mathematical problems, like finding very large prime numbers. 

Since prime numbers are so important in cryptography, it’s likely that quantum computers would quickly be able to crack many of the systems that keep our online information secure. Because of these risks, researchers are already trying to develop technology that is resistant to quantum hacking and on the flip side of that, it’s possible that quantum-based cryptographic systems would be much more secure than their conventional analogues.

Researchers are also excited about the prospect of using quantum computers to model complicated chemical reactions, a task that conventional supercomputers aren’t very good at all. In July 2016, Google engineers used a quantum device to simulate a hydrogen molecule for the first time. Shortly after that IBM has managed to model the behaviour of even more complex molecules. Eventually, researchers hope they will be able to use quantum simulations to design entirely new molecules for use in medicine

Building a functional quantum computer requires holding an object in a superposition state long enough to carry out various processes on them. Unfortunately, once a superposition meets with materials that are part of a measuring system, it loses its in-between state in what's known as decoherence and becomes a boring old classical bit.

Devices need to be able to shield quantum states from decoherence, while still making them easy to read. Different processes are tackling this challenge from different angles, whether it's to use more robust quantum processes or to find better ways to check for errors.

For the time being, classical technology can manage any task thrown at a quantum computer. Quantum supremacy describes the ability of a quantum computer to outperform their classical counterparts.

Google, IBM and a handful of startups are racing to create Quantum computers and achieve Quantum Supremacy.  But the quantum future isn't going to come easily and there's no knowing what it'll look like when it does arrive. At the moment, companies and researchers are using a handful of different approaches to try and build the most powerful computers the world has ever seen. 

In November 2017, when IBM announced it had built a 50-qubit quantum computer. However, it was far from stable, as the system could only hold its quantum microstate for 90 microseconds, a record, but far from the times needed to make quantum computing practically viable. Just because IBM has built a 50-qubit system doesn’t necessarily mean they have cracked supremacy and it definitely doesn’t mean that they have created a quantum computer that is anywhere near ready for practical use.

Quantum computing is by no means a two-horse race. Californian startup Rigetti is focusing on the stability of its own systems rather than just the number of qubits and it could be the first to build a quantum computer that people can actually use. D-Wave, a company based in Vancouver, Canada, has already created what it is calling a 2,000-qubit system although many researchers don’t consider the D-wave systems to be true quantum computers. Intel, too, has skin in the game. In February 2018 the company announced that it had found a way of fabricating quantum chips from silicon, which would make it much easier to produce chips using existing manufacturing methods

Everybody isn't convinced that quantum computers are worth the effort. Some mathematicians believe there are obstacles that are practically impossible to overcome, putting quantum computing forever out of reach. Time will tell who is right.

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A Device That Uses Quantum Effects And Machine Learning To Measure Magnetic Fields More Accurately

Physicists demonstrate magnetometer that uses quantum effects and machine learning to measure magnetic fields more accurately than its classical analogues. Such magnetometer could be used to seek mineral deposits, discover distant astronomical objects, diagnose brain disorders and create better radars.

Researchers from the Moscow Institute of Physics and Technology (MIPT), Aalto University in Finland and ETH Zurich combinedly worked on this and made it the reality. Andrey Lebedev said, When you study nature, whether you investigate the human brain or a supernova explosion, you always deal with some sort of electromagnetic signal. So measuring magnetic fields is necessary across diverse areas of science and technology and one would want to do this as accurately as possible.

This new magnetometer is a revolutionary one, but to understand this let’s first understand what a magnetometer is?
A magnetometer or magnetic sensor is an instrument that measures magnetism either the magnetization of a magnetic material like a ferromagnet or the direction, strength or relative change of a magnetic field at a particular location. It simply means an instrument that measures magnetic fields. A compass is an example of a primitive magnetometer. In an electronics store, one can find more advanced devices of this kind used by archaeologists. Military mine detectors and metal detectors at airports are also magnetometers.

There is a fundamental limitation on the accuracy of such instruments, known as the standard quantum limit. Basically, it says that to double the precision, a measurement has to last four times as long. This rule applies to any classical device, which is to say one that does not utilize the bizarre effects of quantum physics.

It may seem insignificant, but to gain 1,000 times in precision, you would have to run the experiment 1 million times longer. Considering that some measurements take weeks to begin with, chances are you will experience a power cut or run out of funds before the experiment is over

Achieving a higher accuracy, and therefore shorter measurement times is crucial when fragile samples or living tissue is examined. For example, when a patient undergoes positron emission tomography, also known as a PET scan, radioactive tracers are introduced into the bloodstream, and the more sensitive the detector is, the smaller the necessary dose.

In theory, quantum technology enables a measurement's accuracy to be increased twofold by repeating it twice instead of four times as in the case of a classical magnetometer. The paper reported in this story details the first successful attempt to put this principle into practice using a superconducting qubit as the measuring device.

A qubit is a particle that obeys the laws of quantum physics and can occupy two discrete basis states simultaneously in what is known as a superposition. This notion refers to a multitude of "intermediate" states, each of which collapses into one of the two basis states as soon as it is measured. An example of a qubit is a hydrogen atom whose two basis states are the ground and the excited state.

In the study by Lebedev and co-authors, the qubit was realized as a superconducting artificial atom, a microscopic structure made of thin aluminium films and deposited on a silicon chip held in a powerful refrigerator. At temperatures close to the absolute zero, this device behaves like an atom. In particular, by absorbing a specific portion of microwave radiation fed to the qubit via a cable, it can enter a balanced superposition of the two basis states. If the state of the device is then checked, the measurement will detect the ground and the excited state with an equal 50 percent probability.

Superconducting qubits are distinguished by their sensitivity to magnetic fields, which can be used for making measurements. Once a suitable microwave radiation pulse is used to drive the device into a balanced superposition of the ground and excited states, this new state begins to change predictably with time. To track this state change, which is a function of the external magnetic field, the researchers sent a second microwave pulse to the device after a brief delay and measured the probability of finding the qubit in the excited state. This probability, which was calculated over many identical experiments performed in quick succession, indicates the strength of the magnetic field. The precision of this quantum technology surpasses the standard quantum limit.

An actual physical qubit is imperfect. It is a manmade device, rather than a mathematical abstraction. So instead of using a theoretical formula, we train the qubit before making real measurements, This is the first time machine learning has been applied to a quantum magnetometer.

Qubit training consists of making many preliminary measurements under controlled conditions with predetermined delays between pulses and in a range of known magnetic fields. The authors thereby determined the probability of detecting the excited state following the sequence of two pulses for an arbitrary field and pulse delay. The researchers plotted their findings on a diagram, which serves as a fingerprint for the individual device used in the study, accounting for all its imperfections. The point of the sample fingerprint is that the delay times between pulses can be optimized during repeated measurements. 

So far, the prototype device and superconducting qubits work only at about 0.02 degrees above absolute zero, which is defined as −273.15 degrees Celsius. This is some 15,000 times colder than room temperature. Engineers are working on increasing the operating temperature of such devices to 4 kelvins [−269 C]. This would make cooling by liquid helium feasible, making the technology commercially viable.

The prototype has been tested on a static magnetic field, but time-varying or transient fields can be measured in the same way. The research team is already conducting experiments with variable fields, expanding the potential range of applications of their device. 

For example, a quantum magnetometer could be mounted on a satellite to observe astronomical phenomena too faint for classical instruments. Conveniently, the frigid space conditions make cooling somewhat less of an issue. Besides, a system of quantum magnetometers could work as an ultrasensitive radar. Further applications of such nonclassical instruments include MRI scans, mineral prospecting, and research into biomolecule structure and inorganic materials.

Once the first microwave pulse is absorbed by the magnetometer, it enters a superposition of the ground and excited states. This can be visualized by picturing the two basis states of the qubit as the two poles of a sphere, where each other point on the sphere represents some state of superposition. In this analogy, the first pulse drives the state of the qubit from the north pole the ground state to some point on the equator. A direct measurement of this state of balanced superposition would result in the ground or excited state being detected with even odds.

Following the first pulse, the qubit becomes sensitive to the external field. This is manifested as a predictable change of the device's quantum state. It can be pictured as a point rotating along the equator of a sphere. How fast this point rotates, depends on the strength of the external field. This means that by finding a way to measure the angle of rotation X over a known period of time, the field can be quantified.

The main challenge is to distinguish between the different states on the equator: Unless some trick is used, the measurement would return the excited state exactly 50 percent of the time. This is why the physicists sent a second microwave pulse to the qubit and only then checked its state. The idea behind the second pulse is that it predictably shifts the state of the device off the equator, into one of the hemispheres. Now, the odds of measuring an excited state depend on how much the state has rotated since the first pulse, that is, angle X. By repeating the sequence of two pulses and a measurement many times, the authors calculated the probability of an excited state, and thus the angle X and the strength of the magnetic field. This principle underlies the operation of their magnetometer.


Also Read:-How Birds Navigate Their Path? | Quantum Compass

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How Birds Navigate Their Path ? | Quantum Compass

Understanding how birds navigate has fascinated scientists for generations. We finally cracked that odd egg. Its turn out that they have Quantum Compass in their eyes. Like they have sixth-sense kind of thing, but its all can be explained by science.

Half of all bird species migrate to find food as the season turns cold. The exact pathway and location change between species, but they all follow a more or less North-South pattern. That's incredible and it is even true for those that hunt on land. Birds will take the most direct route even that means flying over Big bodies of Water to conserve energy.

But how do these birds know where to go! They don't know how to follow roads or to turn at any landmark. Also, they are a bird, how a bird even know what's a landmark is! They are birds not human. But Birds do have one advantage a built-in compass.

New evidence from two separate studies, one looking at Zebra Finches and the other one European Robins, found that some migrating birds have proteins in their eyes that gives them a sort of " Sixth Sense". It allows them to detect the Earth's magnetic field. That's pretty amazing, right?

In both species, the researchers studied the proteins Cry1, Cry2 and Cry4. These three proteins are called Cryptochromes that are associated with their bodies' internal Circadian Clock. They found that Cry1 and Cry2 levels rise and fall in regular circles during the day. But the level of Cry4 is constant. The simplest explanation is that birds need to produce this protein all the time for some reason. So they look more closely at Cry4.

This protein Cry4 is a peculiar one. It is clustered in a part of the bird's retina, which is very sensitive to blue light. This protein is made from a kind of molecule that some time has an odd number of electrons. The scientists theorize, that as incoming light enters the eye, a photon hits the Cryptochrome proteins and that excites the electron on it. That energy is then transferred between two molecules within the protein yielding two free electrons that are Quantum entangled and therefore, correlated. Scientists theorize the electron's spin form a coherent Quantum state reacts to a weak external magnetic field, for example, the Earth's magnetic field.

Basically, if they are right, these two electrons are reacting to the birds fly through the Earth's magnetic field. As the bird turns or moves, the electrons spin differently, causing different messages to be sent to the bird's brain. The chemical signals that are sent to the bird's brain, allow it to detect the magnetic field within 5-degree accuracy. Theoretically, if they are right.

The Cry4 protein essentially acts like a magnetic compass. Birds always get enough blue light that hit the retina to trigger the electrons' spin to release that chemical any time of a day. Which is insane if you think about it. Because when we humans study Quantum particles it requires supper cooling atoms in a lab environment and not to forget those complex huge machinery. But the inside of a birds eye is warm yet chaotic. So How the heck does they work out Quantum entanglement?

 We really don't know. We also don't know how the chemical signal part of the compass sends messages to the brain or how the birds perceive the magnetic field. We need a bird's eye view, to feel this final piece of the puzzle. More research is obviously needed.

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