You may have bought the most expensive computer for gaming or other heavy use, but it’s weakling compared to a quantum computer, which would cost millions of dollars if you could purchase one.
Quantum computers are machines that use the properties of quantum physics to store data and perform computations. They can be highly advantageous for specific tasks in which they could outperform even the best supercomputers.
Quantum technology works by using the principles of quantum mechanics – the physics of sub-atomic particles – including quantum entanglement and quantum superposition. Quantum mechanics rule the microscopic world; quantum computers are made up of qubits. Unlike a regular computer bit, which can be 0 or 1, a qubit can be either of those or a superposition of both 0 and 1. Such advanced computers increase stability. Most experimental systems rely on heavy shielding and are cooled to operating temperatures approaching absolute zero, making quantum computers very expensive to build and maintain.
Building a working quantum computer is such a daunting venture that many think this can be accomplished only by tech giants and superpowers – something on a scale beyond Israel’s reach.
But now, Israel has joined the quantum computing club. Prof. Roee Ozeri of the Weizmann Institute of Science in Rehovot begs to differ: “One of the world’s first computers, WEIZAC, was built here in 1950 when all Israel had was swamps and camels. Today Israel is a technological empire; there’s no reason we shouldn’t be frontrunners in the quantum computing race.”
In a project reported today in PRX Quantum, Ozeri’s team succeeded in building a quantum computer – one of about 30 such machines globally and one of less than 10 to rely on an advanced technology known as ion traps. An even larger computer is already in the works in Ozeri’s lab, and this one already has a name: In a tribute to WEIZAC, inaugurated at Weizmann back in 1955, the scientists plan to call it WeizQC.
The new computer will make possible a slew of applications, from designing unbreakable codes and predicting market fluctuations to accelerating the development of new drugs, materials, and artificial intelligence systems.
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Ozeri became a pioneer of quantum computing research in Israel some 15 years ago after returning from the US, where he had conducted his postdoctoral studies under the guidance of Nobel laureate David Wineland. “Then, quantum computing was done in university labs,” Ozeri recalled. “But in the past decade, commercial companies such as Google, Amazon, and IBM joined the race to build a quantum computer, while the US, China, and the European Union initiated massively funded strategic programs to advance the field.”
Despite this expansion of research, substantial challenges remain. One of the greatest obstacles is the extreme sensitivity of quantum computers to environmental noise, which stands in the way of building large, complex systems. In a project led by Dr. Tom Manovitz and research student Yotam Shapira, Ozeri’s team addressed this challenge by introducing two innovations, both successfully implemented in the quantum computer the researchers have built-in their lab.
In quantum computing, several different technologies still compete for top ranking. Among the leading contestants are ion traps, systems in which each ion – that is, each electrically charged atom – represents a single qubit. Just as regular bits can move between two states, 0 and 1, ion-based qubits can switch between different states, defined by different flight paths of an electron around the atomic nucleus. Instead of standard electronics, qubit switching in an ion trap is done with lasers.
These qubit-based operations are called logic gates. Complex computations require gates involving more than one qubit, but such operations are sensitive, and even the tiniest environmental noise will cause the system to lose its quantum nature. To prevent this from happening, the Weizmann researchers developed a pattern of laser pulses that keeps the logic gates robust and stable.
Yet even when the gates are robust, the system’s high sensitivity can cause it to accumulate errors that threaten to undo its quantum nature. To correct an error, one must first find it – a task that requires measuring the qubits.
But there is a catch: Measuring constitutes an invasive act that inevitably leads to the loss of the system’s quantum nature. The solution is to measure only some of the qubits, not all of them. In trapped-ion-based computers, the measurements are performed by illuminating the ions and determining the states of the qubits by the resulting, if any, scattering of light.
For their new computer, the Weizmann scientists replaced the light detectors that capture the states of individual ions with a camera-based array that detects all the qubits simultaneously. Then, they concealed some of the qubits from the camera to protect the system’s quantum nature. They also developed a way to overcome the slow-down in data processing associated with camera-based arrays: They added electronic circuits that rapidly read out and process the cameras’ information, speeding up error correction.
The Weizmann computer is a five-qubit machine, roughly the level achieved by IBM’s version when the company first started offering quantum computing as a cloud service. WeizQC, which is currently being built in Ozeri’s lab, is scheduled to work with 64 qubits. It is expected to demonstrate the quantum advantage, which until now has only been achieved by computers built in two labs –at Google and the University of Science and Technology of China.
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