The quantum advantage is the breakthrough that the field of quantum computing is feverishly working towards, where a quantum computer can solve problems that are beyond the reach of the most powerful non-quantum or classical computers.
Quantum refers to the scale of atoms and molecules where the laws of physics we experience break down and different, irrational laws apply. Quantum computers take advantage of this strange behavior to solve problems.
There are some types of problems that are impractical for classical computers to solve, such as breaking state-of-the-art encryption algorithms. Research in recent years has shown that quantum computers have the potential to solve some of these problems. If a quantum computer could be built that could actually solve one of these problems, the quantum advantage would be proven.
I am a physicist working on quantum information processing and control of quantum systems. I believe that this frontier of scientific and technological innovation not only promises breakthrough advances in computing, but also represents a broader rise in quantum technology, including significant advances in quantum cryptography and quantum sensing.
The source of the power of quantum computing
At the heart of quantum computing is the quantum bit, or qubit. Unlike classical bits, which can only be in a 0 or 1 state, a qubit can be in any state that is a combination of 0 and 1. This situation, which is neither just 1 nor just 0, is known as quantum superposition. With each additional qubit, the number of states the qubits can represent doubles.
This property is often perceived as the source of the power of quantum computing. Instead, a complex interplay of superposition, interference, and entanglement emerges.
Interference involves manipulating the states of qubits in such a way that they combine constructively during calculations, enhancing correct solutions and destructively suppressing incorrect answers. Constructive interference is what happens when the crests of two waves, such as sound waves or ocean waves, combine to form a higher crest. Destructive interference is what happens when a wave crest and a wave trough combine and cancel each other out. Quantum algorithms, which are few and difficult to design, create a series of interference patterns that provide the correct answer to a problem.
Entanglement establishes a unique quantum correlation between qubits: No matter how far apart the qubits are, the state of one cannot be defined independently of the others. This is what Albert Einstein famously dismissed as “spooky action at a distance.” The collective behavior of entanglement, managed through a quantum computer, enables computational speeds that are unattainable by classical computers.
Applications of quantum computing
There are a number of potential uses where quantum computing could outperform classical computers. In cryptography, quantum computers pose both an opportunity and a challenge. Most famously, they have the potential to decrypt existing encryption algorithms, such as the widely used RSA scheme.
One implication of this is that today’s encryption protocols must be reengineered to be resistant to future quantum attacks. This recognition has enabled the development of the field of post-quantum cryptography. After a long process, the National Institute of Standards and Technology recently selected four quantum-resistant algorithms and began the process of preparing them for use by organizations around the world in encryption technologies.
In addition, quantum computing can significantly accelerate quantum simulation: the ability to predict the results of experiments conducted in the quantum domain. Famous physicist Richard Feynman predicted this possibility more than 40 years ago. Quantum simulation offers the potential for significant advances in chemistry and materials science, aiding areas such as complex modeling of molecular structures for drug discovery and enabling the discovery or creation of materials with new properties.
Another use of quantum information technology is quantum sensing: detecting and measuring physical properties such as electromagnetic energy, gravity, pressure and temperature with higher sensitivity and sensitivity than non-quantum means. Quantum sensing has numerous applications in fields such as environmental monitoring, geological exploration, medical imaging and surveillance.
Initiatives such as the development of the quantum internet that connects quantum computers are important steps towards bridging the quantum and classical computing worlds. This network can be secured using quantum cryptographic protocols, such as quantum key distribution, which enable ultra-secure communication channels protected against computational attacks, including those using quantum computers.
Despite the growing suite of applications for quantum computing, developing new algorithms that take full advantage of quantum advantage, particularly in machine learning, remains a critical area of ongoing research.
Staying consistent and overcoming mistakes
The quantum computing field faces significant hurdles in hardware and software development. Quantum computers are highly sensitive to unintentional interactions with their environment. This leads to the phenomenon of decoherence, where qubits rapidly fall into the 0 or 1 state of classical bits.
Building large-scale quantum computing systems that can deliver on the promise of quantum acceleration requires overcoming incoherence. The key is to develop effective methods to suppress and correct quantum errors, which is the focus of my own research.
In tackling these challenges, numerous quantum hardware and software startups have emerged alongside established tech industry players such as Google and IBM. This industry interest, combined with significant investment from governments around the world, underscores the collective recognition of the transformative potential of quantum technology. These initiatives are accelerating progress in this field by fostering a rich ecosystem in which academia and industry collaborate.
Quantum advantage emerges
Quantum computing could one day be as disruptive as the arrival of generative artificial intelligence. Currently, the development of quantum computing technology is at a very important point. On the one hand, the field has already shown the first signs of reaching a narrowly specialized quantum advantage. Researchers at Google and later a research team in China demonstrated the quantum advantage of generating a list of random numbers with certain properties. My research team has demonstrated quantum acceleration for a random number guessing game.
On the other hand, if practical results do not materialize in the near term, there is a risk of entering a “quantum winter”, a period in which investments decrease.
While the technology industry strives to gain great advantage in products and services in the near term, academic research is focused on investigating the fundamental principles that underpin this new science and technology. This ongoing fundamental research, fueled by enthusiastic cadres of bright new students like the ones I encounter almost every day, ensures that the field continues to advance.
This article is republished from The Conversation, an independent, nonprofit news organization providing facts and authoritative analysis to help you understand our complex world. The Conversation is trusted news from experts. Try our free newsletters.
Written by: Daniel Lidar, University of Southern California.
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Daniel Lidar receives funding from NSF, DARPA, ARO, and DOE.