Researchers in Japan have created a pure and light diamond for use in quantum computing in a move that could lead to new kinds of hard drives. It’s part of an ongoing effort to use the strange effects of quantum mechanics to hold information. “Unlike our classical computers that operate on binary digits (or ‘bits’), that is, 0’s and 1’s, quantum computers use ‘qubits’ that can be in a linear combination of two states,” David Bader, a computer science professor at the New Jersey Institute of Technology who studies quantum memory, told Lifewire in an email interview. “Storing qubits is more challenging than storing classic bits since qubits cannot be cloned, are error-prone, and have a brief lifetime of a fraction of a second.”
Quantum Memories
Researchers have long hypothesized that diamonds could be used as a quantum storage medium. The crystalline structures can be used to store data as qubits if they can be made nearly free of nitrogen. However, the manufacturing process is complex, and up until now, the diamonds that have been created are too small for practical purposes. Adamant Namiki Precision Jewelry Company and researchers from Saga University claim to have developed a new manufacturing process that can produce diamond wafers that are two inches in size and pure enough for practical applications. “A 2-inch diamond wafer theoretically enables enough quantum memory to record 1 billion Blu-ray discs,” the company wrote in the news release. “This is equivalent to all the mobile data distributed in the world in one day.” Bader said this diamond memory approach relies on storing the qubit as a nuclear spin. “For example, physicists have demonstrated storing a qubit in the spin of a nitrogen atom embedded in a diamond,” he added.
Promising Research
Diamonds are only one way in which quantum computers could store data. Scientists are pursuing two directions for building quantum memories, one using transmission of light and the other using physical materials, Bader said. “Qubits can be represented by the amplitude and phase of light,” Bader added. “Light is also used in quantum computing’s gradient echo memory where the states of light are mapped into the excitation of clouds of atoms, and the light can be ‘un-absorbed’ later. Unfortunately, though, it is impossible to measure both the amplitude and phase without interfering with the light. So we can think about light as a way to transport qubits—much like a classical computer network.” Even more exotic materials than diamonds are being considered. Earlier this year, scientists used a qubit made from an ion of the rare earth element, ytterbium, which is also used in lasers, and embedded this ion in a transparent crystal of yttrium orthovanadate. “The quantum states were then manipulated using optical and microwave fields,” Bader said. Quantum memory could potentially sidestep problems producing large enough hard drives. Bader pointed out that classical computer storage systems of the kind that are in PCs grow linearly in the amount of information stored by classical bits. For example, if you double your hard drive from 512GB to 1TB, you’ve doubled the amount of information you can store, he said. Qubits are “phenomenal” for storing information, and the amount of information represented grows exponentially in the number of qubits. “For instance, adding just one more qubit to a system doubles the number of states,” Bader said. Vasili Perebeinos, a professor at The State University of New York Buffalo who works on a quantum memory, told Lifewire in an email interview that researchers are trying to identify solid-state materials that could be useful for quantum data storage. “The advantage of solid-state quantum memory is in the ability to miniaturize and scale the quantum network device components,” Perebeinos said. However, don’t expect a quantum hard drive in your PC anytime soon. Bader said that “it will take years, and possibly even decades, to build large enough quantum computers with sufficient numbers of qubits for solving real-world applications.”
