The fields of quantum computing and optical communications have a major challenge with managing and storing information at the microscopic level. Traditionally, controlling the behavior of certain elements that are crucial for these processes demands a substantial amount of energy, making it both inefficient and expensive. What's more, the precision with which these elements can be controlled has been far from ideal, limiting the potential for advancements in technologies that rely on quantum mechanics and light-based data transmission.

NTT and partner Nihon University have conducted joint research which has led to the creation of a hybrid state combining photoexcited electrons—electrons that gain energy when a material absorbs photons from light—and gigahertz ultrasonic waves, which have an exceptionally long lifetime of a few milliseconds. Their breakthrough, centered around the use of certain rare earth elements, offers the potential of a new era in quantum optical memory devices, with huge improvements in efficiency and performance.

At the heart of the research is erbium, a rare earth element known for its unique ability to resonate with light at communication wavelengths. Traditional challenges in quantum optics have revolved around the difficulty of controlling the inner electrons of erbium, because the outer, valence electrons interfere by blocking or shielding them. This shielding effect makes it hard to directly access or control the core electrons' properties and behaviors. These core electrons, vital for quantum optical memory, have until now required high-energy inputs for modulation, hindering the development of efficient quantum devices.

NTT and Nihon University's research has successfully manipulated the core electrons of erbium by using ultrasonic waves, which allows for rapid changes in erbium's ability to interact with light. It overcomes previous challenges related to how quickly the electrons lose energy and can efficiently change energy between light and sound across a range of frequencies. This is done using a low amount of electrical power to generate the ultrasonic waves, marking a major advancement towards creating quantum technologies that use less energy.

There are a number of potential uses of the research, notably in the following sectors:

Quantum Computing: By facilitating more effective quantum optical memory devices, quantum computers could tackle complex problems far beyond the capabilities of today's classical computers, driving forward scientific research, cryptography, and more.

Quantum Communication: The advancements have the potential to strengthen quantum communication systems, including quantum cryptography. These systems, built on the principles of quantum mechanics, offer unparalleled security, making them invaluable for sensitive data transmission across global networks.

Sensors and Metrology: The precision control enabled by NTT and Nihon University's research could lead to the creation of highly sensitive quantum sensors, which have the potential to revolutionize fields such as navigation, geological exploration, and medical diagnostics by providing measurements with exceptional accuracy.

Energy-Saving Technologies: At a time when the world is increasingly focused on sustainable solutions, the low-energy requirements of the new technology pave the way for the development of greener technologies across the range of quantum devices.

Optical Amplifiers and Lasers: Improvements in optical amplifiers and lasers, critical for telecommunications and medical imaging, could be enabled by enhancing the manipulation of light and acoustic waves.

The collaboration between NTT and Nihon University has advanced quantum technology, allowing the control of quantum states of electrons with unprecedented precision and efficiency, and offering a future of practical applications that could reshape our technological landscape. More efficient, scalable, and energy-saving quantum devices make for exciting innovation possibilities across computing, communication, sensing, and beyond.

NTT—Innovating the Future of Quantum Computing

Daniel O'Connor

Daniel O'Connor joined the NTT Group in 1999 when he began work as the Public Relations Manager of NTT Europe. While in London, he liaised with the local press, created the company's intranet site, wrote technical copy for industry magazines and managed exhibition stands from initial design to finished displays.

Later seconded to the headquarters of NTT Communications in Tokyo, he contributed to the company's first-ever winning of global telecoms awards and the digitalisation of internal company information exchange.

Since 2015 Daniel has created content for the Group's Global Leadership Institute, the One NTT Network and is currently working with NTT R&D teams to grow public understanding of the cutting-edge research undertaken by the NTT Group.