Researchers at the University of Science and Technology of China have created a new method to verify the location of a device with high precision using quantum mechanics and relativity. This quantum position-verification protocol uses two verifiers located 2 kilometers (1.2 miles) apart to confirm a device's position with a precision of 74.3 meters (244 feet). The method was described in a recent study published in Nature Physics and represents a significant advancement over current systems like GPS, which can be tricked using techniques such as spoofing or relay attacks. This new protocol uses the fundamental principles of physics to ensure that the verification process cannot be easily manipulated or duplicated. The protocol works by having two verifiers located on opposite sides of the position being tested. One verifier sends a quantum state to the device being tested, while both send classical information—like a signal or message—from different directions. The device then uses this classical information to determine how to measure the quantum state it receives and sends back the results. The security of this system is based on two key principles: quantum mechanics limits an attacker's ability to copy or read an unknown quantum state, and relativity limits how quickly information can be exchanged between distant points. This makes it extremely difficult for an adversary to deceive the system. In testing the protocol, the researchers used over 2 kilometers of optical fiber and achieved a very low error rate of 0.27%. The maximum delay in the device’s response was 247.8 nanoseconds, which translated to the 74.3-meter precision. The team also found that each additional nanosecond of delay added about 30 centimeters of uncertainty in the position. To improve the system, the researchers designed a new protocol based on coherent states—light pulses with predictable properties—that allowed for better control of optical signals and reduced losses during transmission. They used conventional lasers and highly stable equipment to ensure the accuracy of quantum states and minimized photon loss using low-loss optical cables. The protocol's success in experiments exceeded theoretical expectations, clearly distinguishing between an honest device and a potential attacker. The researchers believe this method could be applied to cybersecurity, such as verifying the physical location of a server or using a device's location as a security factor. Future work will focus on extending the protocol to longer distances and higher precision, as well as making it more practical and cost-effective for real-world use. The ultimate goal is to integrate quantum techniques into existing positioning systems like GPS, making them more secure and resistant to deception.