Researchers at TCG CREST Solve 16-Year-Old Puzzle in Quantum Computing
Kolkata, 07th November, 2025: A team of young researchers from TCG CREST (Deemed to be University) have cracked a puzzle that has challenged the quantum science community for 16 years. At the heart of the puzzle was a simple but stubborn question – how can quantum computers deliver reliable results for complex problems in lesser time.
The pioneering HHL algorithm introduced in 2009 showed that quantum computers offer potential to solve systems of linear equations exponentially faster than traditional computers. A critical step in the algorithm involves inverting the matrix that occurs in the system of equations, and the ease or hardness in doing so is determined by a metric named the condition number; the larger the condition number, the more the number of times one needs to repeat the algorithm execution to obtain reliable results. Such cases appear more often than not in several potential applications of the algorithm, including describing climate models and molecular simulations for disruptive applications including drug discovery— real-world problems where efficiency matters most. Attempts at addressing the problem either involved expending a significant amount of additional quantum resources or moving away from the HHL algorithm into substantially more complex quantum algorithms, both of which prevented HHL algorithm from realizing its full potential.
The team at TCG CREST (Deemed to be University), based in Kolkata, has now shown how to bypass this roadblock. Their post selection-improved HHL (Ψ-HHL) algorithm subtracts errors from incorrect outputs and quickly isolates the correct answer with almost no additional effort. In doing so, it transforms HHL from a theoretical promise into a tool with real practical value. The work was published in Physical Review Research, a leading physics journal.
This achievement was made possible by a diverse team of young scientists at TCG CREST (Deemed to be University), bringing together expertise from its two key research centers, CQuERE (Centre for Quantum Engineering, Research and Education) and IAI (Institute for Advancing Intelligence). The team includes Peniel Bertrand Tsemo, Akshaya Jayashankar, K. Sugisaki, Sayan Chakraborty, and V. S. Prasannaa.
Commenting on the achievement, Prof. Bhanu Pratap Das, Director, CQuERE, TCG CREST (Deemed to be University), said,
“This breakthrough shows that at TCG CREST, we have the talent and ability to solve problems in the frontiers of quantum computing at the international level. Our young researchers have solved a puzzle that challenged the world for 16 years, showing what is possible when institutions are built around curiosity, rigor, and collaboration. At TCG CREST (Deemed to be University), we are committed to building a research-first ecosystem that empowers talent to solve complex problems. This achievement is a signal that India has both the capacity and the ambition to lead in shaping the next era of quantum science.”
The implications are wide-ranging. For example, in quantum chemistry, the method could help simulate complex chemical reactions with far fewer repetitions, opening the door to faster drug discovery. In materials science, it may enable more precise modeling of advanced materials at the atomic scale. Most significantly, it strengthens the foundations of next-generation quantum computing, where certain algorithms could achieve exponential speedups over classical methods.
“For years, the quantum computing community accepted the limitations of HHL as a roadblock. With Ψ-HHL, we have shown a way to bypass this problem efficiently, which means many more real-world applications can now be unlocked using the algorithm”, explained Srinivasa Prasannaa V, Associate Professor at TCG CREST (Deemed to be University).
Established in 2020, in Kolkata, by The Chatterjee Group (TCG), CREST was conceived as a dynamic force in the global science and technology innovation ecosystem. The institution has made rapid strides in advancing translational research and fostering cross-disciplinary collaboration to address some of the world’s most pressing societal challenges.
TCG CREST has built a strong reputation through its specialized research centres, including the Centre for Quantum Engineering, Research and Education (CQuERE); Institute for Advancing Intelligence (IAI); Centre for High Impact Neuroscience and Translational Applications (CHINTA); Research Institute for Sustainable Energy (RISE); Food Technology & Science Institute (FTSI); and Cancer-related Advanced Research and Education (CARE). CQuERE drives cutting-edge research and training in quantum engineering, fostering global industry-academia collaboration, while IAI offers world-class learning and research in quantitative, computational, and analytical domains.
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