The Inter-University Centre for Astronomy and Astrophysics (IUCAA) in Pune has announced a significant advance in India’s quantum communication capability with the development of an indigenous technology named PhotonSync.

This system is designed to convert standard telecom-grade optical fibres into ultra-stable quantum channels, addressing one of the most persistent engineering bottlenecks in building reliable quantum networks over existing fibre infrastructure.

The achievement comes in the backdrop of 2025 having been observed by UNESCO as the centenary year of quantum mechanics, underlining a broader global push to transition quantum science from the laboratory into field-deployable technologies.

In conventional optical fibre links, the phase and frequency of light signals are highly susceptible to environmental disturbances. Temperature fluctuations along the fibre route, mechanical vibrations, micro-bending of the cable, seismic activity and even routine urban disturbances introduce random phase noise and frequency drifts.

For classical data communications, such variations can be compensated relatively easily by error correction and robust modulation formats. However, quantum communication relies on encoding information in delicate quantum states of photons, where uncontrolled phase noise directly translates to decoherence and loss of quantum information.

This makes long-distance quantum links through ordinary fibres extremely challenging without active stabilisation.

PhotonSync tackles this problem by creating what IUCAA describes as a phase coherent fibre (PCF) link. In essence, the system continuously monitors and corrects the phase and frequency of light propagating through the fibre, maintaining a stable optical reference between the two ends of the link. 

By actively cancelling the phase fluctuations induced by the environment, PhotonSync ensures that photons maintain their precise quantum properties over much longer distances than would otherwise be possible. This stable phase reference is foundational for a variety of quantum communication and precision metrology protocols, including quantum key distribution (QKD), entanglement distribution and clock synchronisation.

According to IUCAA, PhotonSync demonstrates up to a 47.5 dB reduction in phase noise compared to an un-stabilised fibre link. In practical terms, a reduction of this magnitude implies that the residual phase fluctuations are suppressed by a factor of tens of thousands on a power scale.

For quantum applications, this translates into cleaner interference fringes, higher visibility in quantum interference experiments and significantly improved fidelity of transmitted quantum states. Such characteristics are particularly important for protocols that rely on phase encoding or time-bin entanglement, where phase stability directly impacts the security and performance of the system.

The PhotonSync system has been evaluated both on field-deployed optical fibre and in controlled laboratory conditions using fibre spools. In real-world tests, it has been deployed over installed city fibre links up to 3.3 kilometres in length. These tests are critical because they expose the system to realistic variations in temperature, mechanical stress and urban environmental noise.

In addition, the team has tested PhotonSync over fibre spools extending to 71 kilometres, demonstrating its potential for regional-scale quantum networks and long-baseline links. While 71 kilometres is still shorter than national backbones, it provides a strong proof of concept that the technology can scale with further engineering refinement.

A parallel study conducted by researchers at the Jaypee Institute of Information Technology (JIIT) has quantified PhotonSync’s impact on a key performance metric for quantum communication systems: the quantum bit error rate (QBER). QBER measures the fraction of transmitted quantum bits (qubits) that are received incorrectly, and it is a critical parameter for both the security and practicality of QKD.

High QBER not only reduces the net secure key rate but can also indicate vulnerability to eavesdropping or instability in the channel. The JIIT analysis suggests that PhotonSync can reduce QBER by nearly 73 times in comparison with unstabilised fibre links, implying a dramatic enhancement in channel quality and effective secure key throughput.

Such a reduction in QBER has several strategic implications. First, it makes long-distance QKD and other quantum protocols more practical over existing commercial fibre networks, reducing the need for dedicated “perfect” fibres.

Second, it lowers the operational costs and engineering complexity involved in maintaining quantum links, since active stabilisation compensates for a wide range of environmental effects that would otherwise require stringent physical protections.

Third, it strengthens the security margins of quantum communication systems by keeping error rates comfortably below thresholds where advanced quantum hacking strategies might exploit channel instabilities.

From a strategic and industrial perspective, an indigenous system such as PhotonSync supports India’s broader aspirations for technological self-reliance in critical domains. Quantum communication and quantum cryptography are increasingly viewed as national security technologies, with direct implications for diplomatic communications, defence networks, financial systems and critical infrastructure resilience.

Reducing dependence on foreign hardware and proprietary control systems helps mitigate supply chain risks, export restrictions and potential vulnerabilities in black-box components. It also opens up opportunities for export and collaboration with countries seeking trusted quantum infrastructure solutions.

The successful field trials of PhotonSync may serve as a foundation for future pilot networks connecting universities, national laboratories, defence establishments and key government facilities. With further scaling, integration with quantum random number generators, entangled photon sources and advanced QKD protocols, such a system could underpin a layered quantum-secure communication architecture. Over time, it could be extended to inter-city links and form part of a wider national quantum network, complementing satellite-based quantum communication initiatives and testbeds.

Based On New Indian Express Report