Google Willow: How the tech giant made quantum leap in computing

What happened on 9th Dec,2024 could be one of the ‘One small step for Google yet a giant leap for mankind’ moment. Google on that day unveiled its latest quantum chip – Willow. Willow can perform a standard benchmark operation (Random circuit sampling) that would take one of today’s fastest computers 10 25 years in just under 5 minutes. And, by the way, 10 25 is a number vastly greater than the current estimated age of the universe.

For many of us, quantum physics is something that is very difficult to wrap our head around. Quantum mechanics is quite similar to the Indian nod – Is it a Yes? Or a No? Or is it something in between? Quantum states (Called superposition) are very similar to this in that a quantum particle (Called a Qubit) can represent multiple possibilities simultaneously. If the Indian head nod isn’t really helping your understanding, you could also think of this as a coin flipping in mid-air – It could be heads or tails or both all at once. While the systems in nature and the world around us are quantum mechanical in nature, that is usually not how we humans experience it and hence the complexity in comprehension. Well, whether you think you understand it (or not) you can take solace in what the great physicist Richard Feynman said, ‘If you think you understand quantum mechanics, you don’t understand quantum mechanics’.

The advantage that a quantum computer would have over a classical computer is not only its computational speed, but also that it is close to how nature operates. Hence, some applications like weather prediction, climate change, nuclear fusion etc. may only be possible with quantum computers. Beyond that, there are a slew of currently unfathomable applications in pharmaceuticals, material sciences, battery storage etc.

The ‘Hello world’ moment to this development happened in 2019, when Google announced the development of its quantum chip that exhibited quantum supremacy. Meaning this computer was capable of solving a problem that would take a classical computer an impractically long period of time.

For the skeptics, who are imagining how current security & encryption structures (Bitcoin, Blockchain etc.) would collapse after a quantum computer is connected to the internet, Google is ahead of the curve here as well. Google is helping the security community level-up with its post-quantum cryptography & encryption algorithms.

The problem with the qubits though was that it interacts a little too much with its environment (noise) which can cause it to lose signal. This made a quantum computer more error-prone than a classical one and hence practically not useful. In the words of John Preskill from the Institute of Quantum Information and Matter, Caltech – It is a three-way race between Quantum computers, Classical computers and noise!

With Willow, Google has proved exponential quantum error correction – below threshold. This essentially means that as they increase the size of the surface code (Qubits on the wafer) from 3 *3 to 5*5 to 7*7, the qubit stays alive without losing signal for longer rather than shorter meaning exponentially lesser error rather than more. As the first system below this threshold, this has made WHEN to be the most prominent question about quantum computers rather than IF.

While that has some time to go before it becomes commercially relevant or useful, Google has made scientifically interesting simulations on quantum systems already, but these can also be done on classical systems too. Google says it aims to make quantum algorithms that are beyond the reach of classical systems possible while making sure that they solve real-world problems. Google has laid the road-map for the same & is progressing in that direction.

To be sure, this is not the only quantum computer in town. Companies such as IBM, QuEra, Xanadu and others have developed quantum machines too. Microsoft is also innovating with a different kind of qubit called topological qubit which has promise of greater stability. IBM unveiled the 433- qubit Osprey in 2022 and plans to unveil a 1000+ qubit machine by 2026. For reference, Google’s willow has 105 qubits.

This announcement comes at a time when Google has faced criticism for slowing down in innovation and losing relevance, especially as competitors like OpenAI have gained significant attention. Sundar Pichai CEO of Google and Alphabet shared this announcement on Twitter, receiving praise from Space X Founder Elon Musk, Open AI Co-founder Greg Brockman and others.

India also has its very own National Quantum mission approved in April 2023. The mission has a timeline from 2023 to 2031 and includes ambitious goals. The Tata Institute of Fundamental Research (TIFR), Defense Research and Development Organisation (DRDO) and Tata Consultancy Services (TCS) have been at the forefront of quantum computing in India. They successfully tested a 6-bit quantum processor based on superconducting circuit technology in Sep 2024.