How Does a Quantum Computer Work? – Scientific American

Quantum computers are fundamentally different from classical computers in the way they process information. While classical computers use transistors that represent information as either 0 or 1, quantum computers use qubits, which operate based on the laws of quantum mechanics. Qubits can exist in a superposition of states, allowing them to consider all possible routes simultaneously, unlike classical computers that rely on trial and error.

To create a more powerful quantum computer, more qubits are added. Through a property called entanglement, scientists can push multiple qubits into the same state, even if they are not in contact with each other. This increases the computational power exponentially. For example, a two-qubit system can store four possible values, while a 20-qubit system can store over a million.

Quantum computers have the potential to solve complex problems that are difficult for classical computers, such as factoring large prime numbers. This has significant implications for data encryption systems like RSA, which rely on the difficulty of factoring large numbers to ensure security. Quantum computers could potentially break such encryption systems using algorithms like Peter Shor’s algorithm.

However, building practical quantum computers is extremely challenging due to the fragile nature of quantum states. Quantum states are easily disturbed by interactions with the environment, leading to a loss of information through a process called decoherence. Error correction methods are being explored to address this issue, including the use of error-correcting qubits, algorithms designed to handle common errors, and the search for new qubit sources that are more resistant to noise.

Despite the challenges, there have been significant achievements in quantum computing. Google’s 54-qubit quantum computer named Sycamore demonstrated quantum advantage by performing a complex simulation in under four minutes, a task that would have taken the world’s best supercomputer 10,000 years. This achievement showcases the potential power of quantum computing.

However, practical quantum computers are still a long way off, and the technology is advancing slowly. The race for quantum computing capabilities is underway, with support from governments and major companies. The impact of quantum computing on our electronically connected world remains to be seen, but it has the potential to redefine what a computer means and revolutionize various fields of science, technology, and industry.

Source: https://www.scientificamerican.com/video/how-does-a-quantum-computer-work/

What is Quantum Computing? | IBM

Quantum computing is an innovative field that utilizes the principles of quantum mechanics to perform complex computations. Unlike classical computers that use bits, quantum computers employ qubits, which are multidimensional quantum units. These quantum processors are remarkably smaller and more energy-efficient compared to supercomputers.

One crucial aspect of quantum computing is the requirement for extremely low temperatures. While traditional computers rely on fans to cool down, quantum processors need to operate at temperatures just above absolute zero. To achieve this, super-cooled superfluids are employed as they create superconductors. At such ultra-low temperatures, certain materials in quantum processors exhibit a fascinating quantum effect – electrons can flow through them without resistance, making them superconductors.

As electrons pass through superconductors, they form pairs known as Cooper pairs. These pairs possess the ability to transport charge across barriers or insulators via a phenomenon called quantum tunneling. When two superconductors are positioned on either side of an insulator, a Josephson junction is formed, which is utilized as a superconducting qubit in quantum computers.

Control plays a vital role in quantum computing. Josephson junctions, functioning as qubits, can be manipulated through the application of microwave photons. By accurately directing these photons at the qubits, their behavior can be controlled, allowing for the storage, modification, and retrieval of individual units of quantum information.

One of the most remarkable properties of qubits is superposition. Individually, a qubit may not be particularly useful, but it can be placed into a state of superposition, where it represents a combination of all possible configurations. When groups of qubits are in superposition, they can create complex and multidimensional computational spaces. This unique characteristic of quantum computing enables the representation of complex problems in novel ways.

Entanglement is another key aspect of quantum mechanics utilized in quantum computing. It describes the correlation between the behavior of two separate qubits. When qubits are entangled, any change made to one qubit instantaneously affects the other. Quantum algorithms leverage this entanglement to solve complex problems by utilizing the interconnectedness of qubits.

In conclusion, quantum computing represents a significant advancement in the field of computing, employing qubits and the principles of quantum mechanics to perform complex computations. By utilizing superconductors, superposition, and entanglement, quantum computers have the potential to solve problems that are currently intractable for classical computers. As research and development in quantum computing progress, we may witness groundbreaking applications and advancements in various fields.

Source: https://www.ibm.com/topics/quantum-computing

What Is Quantum Computing? | Caltech Science Exchange

Quantum computing is a field of science and technology that aims to develop computers that utilize quantum mechanics principles to perform calculations. Scientists and engineers believe that quantum computers will be capable of solving problems that are currently beyond the reach of classical computers. Additionally, quantum computers are expected to revolutionize communication by introducing completely private communication methods.

One of the main reasons why we want quantum computers is their potential to solve problems that are difficult or impossible for classical computers. Quantum computers have the ability to model and manipulate other quantum systems, which can significantly improve our understanding of physics and influence the design of various technologies. Quantum mechanics plays a role in computer chips, communication devices, energy technologies, scientific instruments, sensors, clocks, and more.

Similar to how people in the 1950s could not have predicted the wide range of applications we have for classical computers today, we may be surprised by the emerging applications of quantum computers. Their unique capabilities have the potential to transform various industries and fields.

So, how does a quantum computer work? Quantum computers share similarities with classical computers in terms of having chips, circuits, and logic gates. Both types of computers operate based on algorithms and use a binary code of ones and zeros to represent information. However, the physical objects used to encode information differ. Classical computers use bits that are in two states, while quantum computers use qubits that can exist in a superposition of states, representing both one and zero simultaneously.

Furthermore, the states of multiple qubits can be entangled, meaning they are linked to each other in a quantum mechanical way. This property of quantum computers, known as superposition and entanglement, gives them capabilities that classical computers do not possess.

Creating qubits can be achieved through manipulating atoms, electrically charged atoms called ions, or electrons. Another method involves nanoengineering artificial atoms, such as qubit circuits, using lithography.

While quantum computers do exist, they are still in the early stages of development. Some technology companies have working quantum computers with fewer than 100 qubits. These computers are kept in a quantum state at extremely low temperatures and shielded from interference.

However, the broader use of quantum computers for practical problems is still years away. The number of qubits needs to be scaled up significantly, which poses challenges in terms of isolating and reducing errors. Researchers are working on strategies to improve the stability of qubits and increase the system’s resilience to errors.

Caltech has played a significant role in shaping the field of quantum computing. Breakthroughs have come from both current and former Caltech scientists and engineers. Caltech centers, such as the Institute for Quantum Information and Matter, the Kavli Nanoscience Institute, and the Joint Center for Quantum Information and Computer Science, have contributed to advancements in the field. Collaboration between researchers at Caltech and around the world is driving progress in quantum computing research and development.

In conclusion, quantum computing has the potential to revolutionize computing and communication. Although practical quantum computers for general-purpose applications are still in the future, ongoing research and technological advancements are bringing us closer to unlocking the full potential of quantum computing.

Source: https://scienceexchange.caltech.edu/topics/quantum-science-explained/quantum-computing-computers

Quantum Computing Is Coming. What Can It Do? – Harvard Business Review

Quantum computing is on the verge of entering the mainstream, with predictions that it could become a $1 trillion industry in the future. Firms like Goldman Sachs are already considering the integration of quantum algorithms into their financial pricing models within the next five years. To understand the significance of this leap, it’s essential to grasp the fundamental nature of computers.

At its core, digital technology is essentially an arithmetic machine. Its ability to perform complex mathematical calculations at an affordable cost has had a profound impact on society. The continuous advancements in both hardware and software have made computing applicable to various products and services, ranging from everyday appliances like cars and dishwashers to smartphones and the internet. Computers have been instrumental in achieving remarkable feats such as space exploration and satellite deployment.

Digital computers operate using binary signals represented by 1s and 0s, commonly referred to as bits or bytes. The complexity of the code directly correlates with the processing power required and the duration of processing. Despite significant advancements, traditional computing devices still face challenges when it comes to certain tasks, even when distributed across numerous machines. One particular area where they struggle is combinatorics, which involves finding the optimal arrangement of items to achieve a specific goal. As the number of items increases, the number of possible arrangements grows exponentially. Current digital computers typically iterate through each permutation to determine the best outcome, often requiring an immense number of calculations. Combinatorics calculations pose significant challenges in fields like finance, pharmaceuticals, and artificial intelligence, acting as critical bottlenecks.

This is where quantum computers come into play. Quantum computers provide a cost reduction for tackling complex combinatoric problems, just as classical computers reduced the cost of arithmetic.

Quantum computers and quantum software are built on an entirely different model of how the world operates. In classical physics, objects exist in well-defined states. However, in the realm of quantum mechanics, objects only assume well-defined states upon observation. Prior to observation, the states and relationships of two objects are matters of probability. From a computing perspective, this means that data is stored and processed in a different manner, using non-binary qubits rather than binary bits. Quantum computers leverage the multiplicity of states in the quantum world to enable faster and more cost-effective combinatoric calculations.

The principles of quantum mechanics can be challenging to comprehend, even for particle physicists, due to the extraordinary properties of the subatomic world it describes. Quantum mechanics provides a better explanation for many aspects of the natural world compared to classical physics, accommodating most of the theories produced by classical physics.

In the context of commercial computing, quantum translates to machines and software capable of performing tasks similar to classical digital computers while excelling in one crucial area: quickly executing combinatorics calculations. The potential of quantum computing extends beyond quantum simulation and encryption, with emerging applications being discovered.

The promise of solving large-scale combinatorics problems faster and more efficiently has attracted billions of dollars in investment. The true potential of quantum computing lies not just in the number of qubits but also in the imaginative, intuitive, and adventurous minds that can harness its power. As the renowned professor and entrepreneur emphasize, maybe it’s not about how many qubits we have; maybe it’s about how many hackers we have.

Source: https://hbr.org/2021/07/quantum-computing-is-coming-what-can-it-do

How Do Quantum Computers Work? : ScienceAlert

Quantum computers are a revolutionary type of computing technology that has the potential to process vast amounts of data by harnessing the principles of quantum mechanics. Unlike classical computers, which operate using binary code consisting of 1s and 0s, quantum computers utilize the probabilistic nature of quantum states.

In classical computing, logical operations are performed based on the definite position of a physical state, typically represented as binary digits. Each state, such as on/off or 1/0, is known as a bit. However, in quantum computing, operations are carried out using the quantum state of an object, which can exist in a superposition. This superposition represents an undefined property of the object before it is measured, similar to a spinning coin that hasn’t landed yet.

Unmeasured quantum states exist in a mixed superposition, and they can also be entangled with the states of other objects. Entanglement means that the final outcomes of these states are mathematically linked, even if we don’t know the specific values yet. By utilizing the complex mathematics of entangled states, quantum computers can solve problems much faster than classical computers.

The potential applications of quantum computers are vast. They can be used to solve complex mathematical problems, create secure encryption codes that are difficult to crack, and predict interactions between particles in chemical reactions.

To build a functional quantum computer, scientists face the challenge of maintaining a quantum state long enough to perform operations on it. This requires shielding the quantum states from decoherence, which occurs when a superposition interacts with the environment and loses its quantum properties, becoming a classical bit.

Different approaches are being explored to overcome this challenge. Some involve developing more robust quantum processes, while others focus on error-checking techniques to ensure the accuracy of computations.

Currently, classical technology is still capable of handling any task that a quantum computer can perform. However, the concept of quantum supremacy refers to the point at which a quantum computer surpasses the capabilities of classical computers. Companies like IBM and Google are actively working to achieve

Source: https://www.sciencealert.com/quantum-computers

Quantum computing and quantum supremacy, explained | WIRED UK

Quantum computing has the potential to revolutionize various fields, including medicine, encryption, communication, and artificial intelligence. Major companies like IBM, Microsoft, and Google are in a race to develop reliable quantum computers, and China has invested billions in this field. Recently, Google claimed to have achieved quantum supremacy, which means a quantum computer outperformed a traditional one for the first time. But what exactly is quantum computing, and how does it work?

Traditional computers use bits, represented by zeros and ones, to perform computations. However, this binary system fails to capture the inherent uncertainty of the universe. At the quantum scale, strange phenomena occur that are explained by quantum mechanics, a field of science developed to understand these phenomena. Quantum mechanics serves as the foundation for physics, chemistry, and biology, and scientists need a better computational method to accurately simulate and handle uncertainty in these domains. This is where quantum computers come into play.

Unlike traditional computers that use bits, quantum computers employ qubits. Qubits can exist in a state called superposition, where they can simultaneously represent both zero and one or any value in between. This is similar to a spinning coin that can land on either heads or tails but can also be in a state where it has a chance of landing on either. Moreover, qubits can be entangled, meaning the state of one qubit is linked to another, even if they are physically separate. This property enables quantum computers to manipulate information containing uncertainty and

Source: https://www.wired.co.uk/article/quantum-computing-explained

What’s So Great About Quantum Computing? A Q&A With NIST Theorist …

The rise of quantum computers has garnered significant attention, particularly due to their potential to break encryption codes and compromise secure messages. To gain insights into the development and underlying concepts of these futuristic machines, it is enlightening to hear from quantum experts like Alexey Gorshkov, a NIST theorist. Gorshkov’s research focuses on the intersection of physics and computer science, offering valuable contributions to the design and understanding of quantum computers.

Unlike classical computers that operate with binary bits representing either 0 or 1, quantum computers utilize qubits, which can exist in superpositions of both 0 and 1 simultaneously. This characteristic enables quantum computers to perform certain calculations exponentially faster, such as attempting various decryption keys to crack encryption. Although simple quantum computers already exist, constructing powerful versions remains a formidable challenge due to the fragile nature of the quantum realm. Even the slightest external disturbances, such as stray electrical signals, can cause a quantum computer to crash before completing useful computations.

Chad Boutin, a public affairs specialist at NIST, interviewed Alexey Gorshkov, delving into the theoretical aspects of quantum computing and shedding light on their potential capabilities. Gorshkov’s work encompasses the proposal of various qubit systems composed of different materials, like neutral atoms, as well as the exploration of quantum algorithms that could run on these computers. Additionally, his research delves into identifying large quantum systems with the potential to outperform classical computers in specific computations. The breadth of Gorshkov’s work is extensive, as he endeavors to unravel the complexities of quantum computing and make incremental progress in this groundbreaking field.

Quantum systems, Gorshkov explains, are entities governed by the principles of quantum mechanics and are particularly observable at small scales. Atoms and electrons are examples of small quantum systems, exhibiting peculiar characteristics such as the ability to exist in two seemingly incompatible states simultaneously. While these small quantum systems are well understood, maintaining these quantum effects becomes more challenging as systems grow larger. In larger systems comprising multiple atoms, the desired quantum effects are easily disrupted by external influences. Therefore, classical physics has been sufficient for comprehending everyday objects governed by classical effects, as these effects overshadow the subtle quantum behaviors.

Gorshkov’s primary research objective revolves around the creation and understanding of large coherent quantum systems. Coherence refers to the preservation of quantum effects even in larger systems. Building large coherent quantum systems that resist environmental disruptions is a formidable task. It entails combining numerous ingredients, such as 300 qubits, while ensuring that the quantum effects remain intact. The creation and simulation of such large coherent systems on classical computers are highly challenging, but it is this coherence that holds the key to unlocking the full power of quantum computers.

The allure of large quantum systems lies in their potential technological applications and their contribution to fundamental physics. Quantum computers hold the promise of revolutionizing secure communication with the establishment of a quantum internet. Moreover, the ability to connect multiple quantum computers would exponentially enhance their computational power. Gorshkov finds these possibilities captivating and recognizes that many scientists share his fascination with exploring the frontiers of quantum computing.

When asked about his personal interest in quantum research, Gorshkov recalls his initial exposure to the field after his junior year in college. He was immediately drawn to the interdisciplinary nature of quantum research, which combines mathematics, physics, computer science, and collaboration with experimentalists. The interconnectedness between these fields allows for the transfer of ideas and insights, resulting in a harmonious amalgamation of knowledge and progress.

Addressing concerns about the potential vulnerabilities of encryption to quantum computers, Gorshkov emphasizes that not all encryption will be compromised. Certain encryption protocols are based on mathematical problems that are susceptible to quantum computers, while others remain secure. NIST’s post-quantum cryptography project aims to develop encryption algorithms that can withstand attacks from quantum computers.

In terms of potential applications that excite Gorshkov, simulation stands out as a notable prospect. Quantum computers have the potential to simulate complex phenomena in chemistry, materials science, and nuclear physics. These simulations could unravel the intricacies of large molecules with vast electron clouds, enabling advancements in fields such as drug discovery. Additionally, quantum computers might offer improved solutions to classical optimization problems that pose significant challenges for classical computers. For instance, finding more efficient ways to direct shipments in complex supply chain networks could be addressed by quantum computers, although the extent of their advantage over classical methods remains uncertain.

Regarding our knowledge of the capabilities of powerful quantum computers, Gorshkov explains that researchers possess a theoretical understanding of the microscopic quantum theory that underlies qubits. By combining mathematical, physical, and computer science principles, experts can describe the potential capabilities of quantum computers when qubits are interconnected. While there are skeptics who propose unknown effects that might disrupt coherence in large systems, the way to disprove these theories is through experiments conducted on progressively larger quantum systems.

When asked about his research goals, Gorshkov expresses his desire to witness the development of a useful quantum computer. He finds himself in an exhilarating era, reminiscent of his childhood enthusiasm for solving math problems. The current problems in quantum computing provide the same level of enjoyment and excitement, and he anticipates significant breakthroughs in the field.

Finally, Gorshkov highlights the importance of working at NIST, a measurement-focused laboratory, for quantum research. NIST has renowned experimentalists who contribute to the advancement of quantum computing. The institution provides ample resources for conducting exceptional scientific research, and working in a public institution allows researchers to serve society effectively. Quantum computing originated from NIST’s endeavors to develop improved clocks, with scientists like Gorshkov building upon the impressive control over ions and neutral atoms achieved through measurement techniques. Additionally, Gorshkov mentions that the measurement aspect is at the core of quantum computing, and researchers are actively working on measuring the quantum advantage to quantify the superiority of quantum computers compared to classical counterparts.

Source: https://www.nist.gov/blogs/taking-measure/whats-so-great-about-quantum-computing-qa-nist-theorist-alexey-gorshkov

How a quantum computer actually works – Protocol

Quantum computing is the next step in technological advancement, harnessing the quantum properties of materials to process information. Unlike classical computers that use bits with definite values of 0 or 1, quantum computers use qubits, which are quantum objects with undefined properties. Qubits can exist in a superposition state, representing a combination of 0 and 1, until they are measured and interact with their environment, which defines their final value.

Interference plays a crucial role in quantum computing. By manipulating the starting conditions and interactions of multiple qubits, interference effects can be created, increasing the probability of the qubits arriving at a specific final state. Designing quantum algorithms involves creating interference patterns that favor the measurement of states encoding the solution to a problem.

Superposition, interference, and a third phenomenon called entanglement are the key elements that give quantum computers their computational power. Entanglement occurs when quantum particles interact and share properties, allowing measurements on one particle to influence subsequent measurements on entangled particles, even when physically separated. This phenomenon is difficult to replicate in classical computers and is necessary for achieving computational speedup.

Quantum computers offer advantages in certain types of problems where it is challenging to find the solution but easy to verify it. For example, factoring large numbers, a process crucial for encryption, is currently inefficient for classical computers but can be performed efficiently using quantum algorithms like Shor’s algorithm. The interference effects of qubits allow the algorithm to distinguish the right answer from incorrect ones.

While Shor’s algorithm is one of the three applications where quantum computers are expected to outperform classical machines, including Grover’s algorithm for searching unstructured databases and simulation of quantum systems, there is still much unexplored territory in quantum computing. Industries such as military, intelligence, pharmaceuticals, and information processing are showing great interest, and algorithm design is an ongoing area of exploration.

The timeline of quantum computing showcases notable milestones in the field. In 1981, physicist Richard Feynman outlined the potential advantages of computing with quantum systems. In 1994, Peter Shor presented an algorithm that could efficiently factor large numbers, surpassing classical algorithms. Lov Grover proposed a search algorithm with quantum advantage in 1996. In 2019, Google claimed quantum supremacy, demonstrating a quantum computer’s ability to solve a specific problem faster than any classical computer.

Quantum

Source: https://www.protocol.com/manuals/quantum-computing/how-a-quantum-computer-works

How Do Quantum Computers Work? – Science World

Quantum computers operate on the principles of quantum mechanics, which involve interactions at a very small scale. To understand quantum computers, it’s important to start with an open mind and a basic understanding of how regular computers work.

Normal computers break down big tasks into small parts and use binary, represented by 0s and 1s, which are called bits. The binary digits relate to the computer sending an electric current through a wire or not. For example, when you press the letter ‘A’ on your keyboard, it is represented by a 7-digit combination of 0s and 1s: 1000001. Each wire either sends current (1) or does not send current (0).

Once the computer receives this information, it processes it using binary logic and various operations like AND, OR, NOT, and XOR, which are implemented using electronic switches called transistors.

Now, let’s explore how quantum computers work. Quantum computers utilize two fundamental concepts of quantum mechanics: superposition and entanglement.

Superposition is a quantum mechanical effect where a quantum bit, known as a qubit, behaves as if it can be in multiple states simultaneously. In regular computers, a bit can be either 0 or 1, but in quantum computers, a qubit can exist as both 0 and 1 at the same time. This is due to the wave-particle duality of quantum objects, which exhibit behaviors resembling waves.

Entanglement, the other concept, involves a special type of superposition between two or more qubits. Entangled particles are correlated in a powerful way. While we focus on superposition here, entanglement will be discussed in a future post.

To understand superposition better, imagine two doors in front of you, with someone saying your friend is behind one of them. In the quantum world, your friend behaves as if they are behind both doors simultaneously until you open one. Unlike at the human level, where you can’t be both at work and not at work, this quantum behavior occurs at the particle level.

However, superposition is only one part of the game; the other part is measurement. When you open the door, one of the possibilities becomes true, and the other collapses. For example, if your friend is not behind the door you open, you know they must be behind the other door. Quantum measurement is random, making quantum mechanics probabilistic. But scientists have found ways to utilize this randomness for useful tasks.

So how does superposition benefit quantum computers? Quantum computers operate differently from regular computers. Superposition enables quantum computers to explore new moves when processing information. Like waves interfering to create a new wave, quantum computers exploit interference. When a calculation is performed on a quantum computer, it simultaneously explores different paths due to superposition. By carefully manipulating the information, the paths leading to wrong answers destructively interfere, while the paths leading to the right answer constructively interfere, allowing the quantum computer to calculate the correct answer efficiently.

Quantum computers excel in specific tasks such as searching databases, factoring numbers, and simulating molecular and chemical processes. These tasks would take regular computers millions of years to complete, but a quantum computer can solve them in just a matter of seconds.

Quantum computing is a fascinating field that opens up new possibilities for solving complex problems efficiently. If you’re interested in learning more, be sure to visit the Ready to leap into quantum? exhibition at TELUS World of Science, running until February 26. Don’t miss out!

Source: https://www.scienceworld.ca/stories/ho-do-quantum-computers-work/

How Does a Quantum Computer Work? – Physics Stack Exchange

A quantum computer operates using quantum states instead of classical states. Quantum states are combinations of classical states. In classical computing, a computer takes a specific input and produces an output. In quantum computing, however, the input can be a combination of all classical inputs. For example, if there are n classical inputs, the quantum computer can represent the input as a combination of all these inputs simultaneously.

After performing the computation, the quantum computer processes this combination of all inputs into a combination of all possible outputs. Ideally, this would allow us to compute all the outputs of a function as quickly as computing just one output. However, there’s a quantum caveat. When observing the answer, instead of seeing all possible outputs, we see only one output with a certain probability.

This might make it seem like we’ve only computed the function once, similar to classical computing. However, with clever algorithms, we can still leverage the power of quantum computers. Suppose we are interested in a function that depends on all the outputs of the computation. By designing an algorithm, we can transform the combination of all outputs into the desired function, which depends on all the answers.

In classical computing, finding this function might require computing every output individually. However, a quantum computer can potentially compute it once using its ability to process combinations. This is where the quantum computer gains its advantage over classical computers.

It’s important to note that the described approach is a simplified explanation and does not capture the full complexity of most quantum computing applications. The actual workings of quantum computers often involve intricate mathematical concepts. Nevertheless, the fundamental idea remains that quantum computers can outperform classical computers by efficiently processing combinations of inputs and outputs.

Source: https://physics.stackexchange.com/questions/12460/how-does-a-quantum-computer-work