Physicists enable qubits to chat in light at room temperature in a quantum leap
Researchers at the Institute of Science and Technology in Austria (ISTA) have achieved a major milestone in quantum computing after obtaining a complete optical readout of superconducting qubits.
This will help in building scalable quantum computers that are robust, operate at room temperature, and at a much lower cost, a press release said.
Quantum computers are the next frontier of computing, allowing calculations to occur at exponential rates compared to classical computers.
At the core of the quantum computer is the quantum bit or qubit that can occupy multiple states at once, allowing it to carry out multiple calculations at once, as against its binary counterpart, the bit.
To achieve this state, scientists use properties of materials, such as their superconductivity. However, these states can only be reached at temperatures close to absolute zero, which then requires extensive cryogenic cooling infrastructure, increasing computational costs.
Using fiberoptics with quantum hardware
Even as work is ongoing on building scalable quantum computers, some research groups are working to build the necessary network that it will need to operate. Just as the internet requires an extensive fiber optic network to operate, quantum computers also need a network that can transport qubits.
Rolling out a cryogenically cooled network globally is impossible, so scientists are also working on using the existing fiber optic network to relay quantum information.
Superconducting qubits are electrical by nature but have low bandwidth. They can transmit little information over time and get easily overwhelmed by noise. On the other hand, optical signals are high-bandwidth signals that can propagate with minimal losses.
While this makes them ideal for qubit readouts, the challenge is communicating between these two and translating the optical signals to qubits and back.
Microwaves to the rescue
“Ideally, one would try to get rid of all electrical signals, as the required wiring transports a lot of heat into the cooling chambers where the qubits are. But this is not possible,” explained Thomas Werner, a PhD student at ISTA who was involved in the work.
The researchers turned to an electro-optic transducer that converts optical signals to microwave frequency, which qubits can understand. When the microwave is directed toward a qubit, the qubit reflects its back, thereby establishing communication with the transducer and connecting it to the outside world.
“We showed that we can send infrared light close to the qubits without making them lose their superconductivity,” added Werner. The approach also helps overcome the limitations of conventional readout systems that are error-prone and need multiple corrections.
“By using the electro-optic transducer to disconnect the qubits from the electrical infrastructure, we were able to replace all the remaining parts of the setup with optics,” said Werner, highlighting the efficiency and cost advantages of the approach.
“This new approach might allow us to increase the number of qubits so they become useful for computation. It also lays the foundation for building a network of superconducting quantum computers connected via optical fibers at room temperature,” concluded Georg Arnold, former PhD student at ISTA, who was also involved with this work, in the press release.
Source: Interesting Engineering
Physicists enable qubits to chat in light at room temperature in a quantum leap
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