RRI Technique Yields Certified Randomness with One Qubit
Context
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Researchers from the Raman Research Institute (RRI), Bengaluru, led by Prof. Urbasi Sinha, have demonstrated that certified quantum randomness can be generated using just one qubit on IBM’s superconducting quantum computers available on the cloud.
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This marks a step toward secure quantum random number generation feasible even on today’s noisy quantum devices.
Background
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Randomness is vital for applications such as:
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Cryptography – securing sensitive data.
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Scientific simulations – modeling complex systems.
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Secure communications and data encryption.
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Classical random number generators are pseudorandom—they rely on algorithms and are predictable if the initial seed is known.
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True random number generators based on physical processes (like radioactive decay or electronic noise) face challenges:
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Hardware degradation.
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Potential manufacturer manipulation.
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Difficulty in certifying true randomness.
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Quantum Approach to Randomness
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Quantum mechanics inherently allows fundamental randomness — e.g., the outcome of measuring a qubit’s spin.
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Traditionally, Bell inequality violations have been used to certify quantum randomness, but these require:
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Two entangled qubits.
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Spatial separation, making them impractical on a single quantum computer.
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The Leggett–Garg Inequality (LGI)
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Provides a temporal alternative to Bell tests.
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Instead of spatially separated systems, it compares measurements made at different times on the same system.
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Violation of LGI, while satisfying the “no signalling in time” (NSIT) condition, certifies that the randomness is truly quantum.
The RRI Experiment
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Objective: To test whether modern cloud-based quantum processors (like IBM Quantum) can generate certified random numbers.
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Method:
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Used only one qubit and single-qubit rotation gates.
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Measured the qubit at three different times.
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Checked for violation of the LGI and satisfaction of NSIT.
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Applied error mitigation techniques to control classical noise.
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Results:
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Consistent LGI violations observed on IBM’s Brussels backend.
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Slight deviations from theory due to hardware noise.
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Certified randomness confirmed by quantum mechanical principles.
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Significance and Implications
1. Practical Quantum Randomness
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Certified random numbers can now be generated on existing quantum hardware.
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Requires only a single qubit and simple circuits.
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Feasible for end-users accessing quantum computers via cloud platforms.
2. Security and Trust
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Device-independent certification adds credibility.
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Classical systems cannot fake this randomness — enhancing data security and cryptographic reliability.
3. Error Mitigation Importance
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Readout error correction and other mitigation tools improved results.
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Reinforces the need for noise control in Noisy Intermediate-Scale Quantum (NISQ) devices.
4. Foundational Physics Impact
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Confirms Leggett–Garg inequality violation within a quantum computing context.
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Provides experimental support for quantum theory in new domains.
5. Benchmarking Future Qubits
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The same technique can act as a benchmarking tool for evaluating new qubit registers and quantum hardware performance.
Way Forward
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Further improvements needed to reduce noise and improve theoretical accuracy.
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Potential for developing commercial quantum random number generators.
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Strengthens India’s position in quantum computing research and secure information technologies.
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