Quantum technology could one day make communications more secure and sensors far more sensitive.
But there is a major obstacle: many quantum systems only work at extremely low temperatures, requiring large, expensive cooling equipment.
MIT researchers have now developed a small magnetic device that can produce strongly linked microwave signals at room temperature.
The advance could help make quantum-inspired secure communications, radar and sensing technologies cheaper and easier to use outside laboratories.
The technology works with microwaves, the electromagnetic signals widely used in wireless communications and radar.
Scientists have long known how to create pairs of microwave signals whose properties are closely connected.
These correlated signals are useful because information carried by one signal can be recovered using its matching partner.
Traditionally, researchers produce such signals using superconducting circuits containing components called Josephson junctions.
But superconducting devices must operate at temperatures close to absolute zero. Maintaining these conditions requires bulky and energy-hungry cooling systems.
The MIT team found a way around this problem by using magnetism instead.
Their device contains a thin magnetic film placed inside a metal cavity that traps microwave energy. When microwave energy enters the system, it interacts with magnetic excitations called magnons, which can be thought of as tiny packets of magnetic energy.
By carefully controlling this interaction, the researchers created hybrid waves that combine properties of magnons and microwave photons. The system can then split an incoming microwave signal into two strongly correlated signals with different frequencies.
Each signal appears random when examined by itself, but the relationship between the pair remains closely synchronized. Importantly, their frequencies are different, allowing the two signals to be separated and used independently.
The researchers demonstrated the potential for secure communication by encoding a small image into one of the microwave signals. They were able to recover the image using the matching partner signal.
Without access to that partner, an outside observer would have difficulty extracting the encoded information because the individual signal appears random.
The researchers say the approach could eventually support communication systems that are more resistant to interference. If noise or unwanted signals distort a transmission, the correlated partner could help the receiver identify and recover the original message.
The technology could also have applications in highly sensitive radar and sensing systems, where detecting extremely weak signals is important.
Another possible use is quantum simulation. Quantum simulators are designed to reproduce complicated interactions between particles that can be difficult for conventional computers to model. Scientists hope such systems could eventually help with tasks including discovering new materials and medicines.
Producing correlated microwave signals without extreme cooling could make these technologies much cheaper and easier to scale.
The researchers emphasize that their current demonstration operates in a classical, quantum-inspired regime rather than being a complete room-temperature quantum communication system. However, they believe the platform could provide an important foundation for future technologies that eventually use genuinely quantum effects.
The team now plans to develop a more scalable version of the device and investigate other applications. If successful, the technology could help move advanced microwave communication and sensing systems out of specialized laboratories and closer to practical, everyday use.
