Moving beyond classical computers

A Google research paper describing one of the most powerful quantum computers in human history was leaked on NASA’s website on Sept. 20. In 200 seconds, the quantum computer executed tasks that would take the fastest of today’s computers 10,000 years to compute. 

Google was referencing an experimental type of computer that exploits complicated subatomic physics to run certain programs differently than the ‘classical’ computers we use every day. Unlike regular computers, which use bits to encode either a one or a zero, the primary unit of quantum computers is the qubit, a piece of information that can be zero, one, or both. With only 56 qubits, Google’s quantum computer achieved quantum supremacy, the point at which a quantum computer can complete a task faster than its classical counterpart. 

While the paper was swiftly removed from NASA’s website, the idea of a quantum computer is not as shocking as it seems, since such machines are limited to algorithms that take advantage of quantum properties. An enormous amount of work went into the Google project, which modelled a quantum system, an impractical task that can be done in a classical computer very slowly.

Despite this, quantum computing has the potential to change how we use computers in general. Claude Crépeau, a professor in the Department of Computer Science and a quantum computing pioneer, noted the importance of the leaked Google paper.

“It is a milestone,” Crépeau said in an interview with The McGill Tribune. “With limited technology [today], we can make things [that would have been] unbelievable 20 years ago.” 

Today’s technology is the result of companies like Microsoft and Google shovelling millions of dollars into projects. Companies are investing in quantum computing at a large scale because they already know of applications to take advantage of its strengths. One such applications is in cryptography, the field concerned with protecting information through code. Quantum computing could be used to dismantle current cryptographic systems, but it could also create amazing ones.

The internet relies on cryptography for secure data transfer. Public key cryptography is the most common cryptographic system in use and is based on the idea that finding a large number’s prime factors is computationally difficult, making it harder for hackers to access private information. Quantum computers could, however, pose a threat for cryptography and internet security, since they could potentially guess key combinations very efficiently

While quantum computing might be the biggest problem that cryptography faces, it could also be its saviour. By using quantum computers, computer scientists will be able to develop quantum secrecy, a stronger way of protecting information.

“In 50 years, I cannot guarantee public key cryptography will work,” Crépeau said. “In 100, it will probably not work. Quantum secrecy is perfectly valid, […] unless we are completely wrong about quantum physics, which would be a revolution.” 

Investigating quantum secrecy for cryptographic use could have profound implications. It may not affect all cryptographic communication, but it could still allow us to keep our most important secrets safe. There are many other promising quantum applications, such as simulating chemical interactions and financial markets, in addition to breaking old and creating new cryptographic systems. Researchers still need to create the hardware to implement quantum computing, which may still take several decades.

“[I can say with] 75 per cent certainty, something practical [will develop] in 20 years,” Crépeau said. “[But] I could be completely wrong about all that.”  

According to Crépeau, we could soon be looking at a world where people use quantum computers to execute tasks impossible to do otherwise. With the right breakthroughs in hardware, the potential applications for quantum computers are as limitless as they seemed for classical computers in the mid-20th century. 

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