story so far: On December 13, Ajai Chowdhry, chairman of the newly established National Quantum Mission Management Committee, said that India plans to launch a quantum satellite “within 2-3 years for quantum communications.”
What is the National Quantum Mission?
The National Quantum Mission (NQM) is a Department of Science and Technology program that aims to accelerate the application of quantum physics in the development of next-generation communications and sensing systems.
The development of computers has changed the course of human history since the mid-20th century. Thanks to ongoing advances in this field, humans have access to telecommunications, weather forecasting, drug discovery programs, search and rescue programs, artificial intelligence, and more.
But many of these advances are approaching saturation point because the physical phenomena on which they are based, known as classical physics, are reaching performance ceilings. Today, scientists around the world are building new devices that perform the same function, but using quantum physics. Since the rules of quantum physics allow for results from classical physics as well as “extra” results not found in the classical paradigm, new devices are expected to have new capabilities.
The federal cabinet approved the NQM in April 2023 at a total cost of Rs 6,000 crore and will be implemented from 2023 to 2031.
What is a quantum satellite?
Quantum satellite is the term for communications satellites that use quantum physics to protect their signals.
Communications is a broad term that refers to the technology of sending and receiving signals. An important part of these technologies is security: preventing bad actors from intercepting messages traveling long distances across multiple networks.
The emergence of quantum computers threatens the technology currently used to protect information. Fortunately, quantum physics is also paving the way for new forms of protection, and quantum satellites promise to facilitate them.
How to protect message security?
Suppose Anil and Selvi are standing at opposite ends of the playground and want to talk to each other. The easiest way is to shout or wave. There was a third man, Kaushik, standing in the middle of the ground trying to eavesdrop on the conversation. If Anil and Selvi shout or use gestures, Kaushik will have no trouble intercepting their messages, but not if they communicate via WhatsApp.
Messages in WhatsApp are encrypted. Encryption means that the message is written in a password before transmission. When the recipient receives the message, they use their knowledge of the code to decrypt the message and read it. If a bad guy like Kaushik somehow intercepted the message, he wouldn’t be able to read it without knowing the code.
For example, in the Caesar cipher, the letters of the alphabet are offset by a fixed number. If the number is 5, the word BIRDS FLY AWAY becomes GNWIX KQD FBFD.
This paradigm is called password security. Its power lies in hiding the key to cracking the code behind extremely difficult mathematical problems. Anil and Selvi’s device has solved this problem. However, if Kaushik wanted it, he would have to solve the problem on a computer first—the harder the problem, the more time (or more computing resources) he would need.
Modern computers can quickly crack the Caesar cipher by repeatedly trying all possible keys (1-26) until the text becomes clear. But even the most powerful supercomputers won’t be able to crack today’s best Advanced Encryption Standard passwords in a lifetime. However, quantum computers may be able to do better.
How does quantum physics protect information?
Quantum cryptography uses the principles of quantum physics to protect the security of messages. Its most famous type is Quantum Key Distribution (QKD).
In the previous example, Anil used a password to encrypt or “lock” his message, and Selvi had the key to decrypt and read the message. QKD cares about sharing the key with Anil and Selvi so that if Kaushik eavesdrops on the transmission, everyone will find out and stop sharing.
Quantum physics can reveal eavesdropping in different ways. One is quantum measurement – measuring the properties of quantum systems, such as photons (subatomic particles of light). According to the rules of quantum physics, quantum measurements change the state of the system. If information about the key is encoded in a stream of photons (which have two states, one representing 0 and the other representing 1), and Kaushik captures and measures them to find it, then the state of the photon will change, Anil and Selvi will know that the key has been compromised.
Another approach is to use quantum entanglement: when two photons are entangled, any change in one particle immediately changes the other. (This is necessarily a simple description.)
Since the key will be lost regardless of Kaushik’s technical capabilities, QKD is said to provide unconditional security.
Has QKD been implemented?
Ravindra Pratap Singh of the Physical Research Laboratory in Ahmedabad wrote in 2023 that standards for different QKD protocols and the technology required to implement them as designed are still ten years away. year time. Nonetheless, China currently operates the world’s largest QKD network, with three quantum satellites and four ground stations.
Experts are also trying to implement QKD over longer distances. In the two decades since its experimental demonstration in 1992, reliable transmission distances over fiber optic cables or free space have increased to hundreds of kilometers.
In 2013, Chinese researchers reported that they had implemented QKD between a ground station and a hot air balloon (carrying an instrument payload) traveling at an altitude of 20 kilometers. This demonstration supports the case for quantum satellites.
In an October 2024 study, researchers at the Raman Institute in Bangalore reported that the Indian Astronomical Observatory in Hanle, Ladakh, provides optimal atmospheric conditions for transmitting data from satellite-based QKD systems. The expected signal loss is 44 dB, while the signal loss in the Chinese experiment was 50 dB.
“Our main signal will be at 810 nm, while the uplink and downlink will use wavelengths of 532 nm and 1550 nm respectively,” Satya Ranjan Behera, lead author of the paper, told the Ministry of Science and Technology. The planned beam distance is 500 kilometers.
Are there any disadvantages to QKD?
Because QKD on paper can be very different from QKD in the real world, the NSA recommends using post-quantum cryptography instead of quantum cryptography. Its criticisms focus on five limitations:
(i) “QKD does not provide a method to verify the source of a QKD transmission”;
(ii) “Because QKD is hardware-based,” the QKD network cannot be easily upgraded or patched;
(iii) “QKD increases infrastructure costs and insider threat risk” and “eliminates many use cases”;
(iv) “The actual security provided by the QKD system is not the unconditional security theoretically provided by the laws of physics… but the more limited security that can be achieved through hardware and engineering design”; and
(v) Because eavesdroppers can cause a transmission to stop, they can deny the intended user access to the transmission (also known as a denial of service attack).
Post-quantum cryptography refers to cryptography that uses more advanced classical encryption techniques to resist attacks from quantum and classical devices.
Quantum physics also imposes some limitations. For example, non-quantum information can be amplified before being transmitted over long distances, while the non-copy theorem prohibits the amplification of quantum information.
Published – December 20, 2024 at 06:00 AM (US Standard Time)