UPSC Prelims Practice Questions — Physicists are finding new ways to make electrons act strangely
Q1. The 2024 experimental demonstration of the fractional quantum anomalous Hall effect in rhombohedral multilayer graphene, published in Nature, was led by a research group based at which one of the following institutions?
- A. Massachusetts Institute of Technology (MIT)
- B. University of Manchester
- C. Chinese Academy of Sciences
- D. Max Planck Institute for Solid State Research
Q2. In the term 'Fractional Quantum Anomalous Hall Effect', the word 'anomalous' most precisely denotes which one of the following?
- A. That the fractionalized-charge physics arises without any externally applied magnetic field
- B. That the charge carriers are quasiparticles rather than electrons
- C. That the Hall conductance is quantized in fractional rather than integer steps
- D. That the effect occurs only at room temperature rather than near absolute zero
Q3. Consider the following statements comparing the integer quantum Hall effect (IQHE) and the fractional quantum Hall effect (FQHE):
1. The IQHE shows Hall conductance quantized in integer multiples of e²/h, whereas the FQHE shows quantization at fractional multiples of e²/h.
2. The FQHE was experimentally discovered before the IQHE.
3. The FQHE was observed at a lower temperature than that used in the original IQHE observation.
Which of the statements given above is/are correct?
- The IQHE shows Hall conductance quantized in integer multiples of e²/h, whereas the FQHE shows quantization at fractional multiples of e²/h.
- The FQHE was experimentally discovered before the IQHE.
- The FQHE was observed at a lower temperature than that used in the original IQHE observation.
- A. 1 and 2 only
- B. 1 and 3 only
- C. 2 and 3 only
- D. 1, 2 and 3
Q4. The integer quantum Hall effect was first observed in 1980 in a two-dimensional electron system realised at which one of the following?
- A. A semiconductor–oxide interface
- B. A superconducting Josephson junction
- C. A graphene–hexagonal boron nitride moiré superlattice
- D. A dilute ultracold atomic gas in an optical lattice
Q5. The Nobel Prizes recognising both the integer and the fractional quantum Hall effects were conferred by which one of the following bodies?
- A. The Royal Swedish Academy of Sciences
- B. The Norwegian Nobel Committee
- C. The Karolinska Institute
- D. The Swedish Academy
Q6. Consider the following statements about the Nobel Prizes in Physics linked to quantum Hall physics:
1. The 1985 Nobel Prize, for the integer quantum Hall effect, was awarded solely to Klaus von Klitzing.
2. The 1998 Nobel Prize was shared by Robert Laughlin, Horst Störmer and Daniel Tsui.
3. Robert Laughlin's share of the 1998 prize was for the experimental discovery of the fractional quantum Hall effect.
Which of the statements given above is/are correct?
- The 1985 Nobel Prize, for the integer quantum Hall effect, was awarded solely to Klaus von Klitzing.
- The 1998 Nobel Prize was shared by Robert Laughlin, Horst Störmer and Daniel Tsui.
- Robert Laughlin's share of the 1998 prize was for the experimental discovery of the fractional quantum Hall effect.
- A. 1 and 2 only
- B. 2 and 3 only
- C. 1 and 3 only
- D. 1, 2 and 3
Q7. Consider the following statements about graphene and moiré superlattices:
1. Graphene is a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice.
2. Formation of a moiré superlattice always requires stacking two chemically different materials.
3. Moiré superlattices can exhibit emergent properties that are absent in their parent materials.
Which of the statements given above is/are correct?
- Graphene is a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice.
- Formation of a moiré superlattice always requires stacking two chemically different materials.
- Moiré superlattices can exhibit emergent properties that are absent in their parent materials.
- A. 1 and 2 only
- B. 1 and 3 only
- C. 2 and 3 only
- D. 1, 2 and 3
Q8. In graphene's honeycomb lattice, each carbon atom is covalently bonded to how many nearest-neighbour carbon atoms?
- A. Two
- B. Three
- C. Four
- D. Six
Q9. With reference to fractionally charged quasiparticles and anyons, consider the following statements:
1. In the ν = 1/3 fractional quantum Hall state, the quasiparticles carry a charge of e/3.
2. Anyons are excitations whose exchange can produce a phase different from ±1.
3. Non-Abelian anyons have been proposed as a basis for fault-tolerant topological quantum computation.
4. Fractionally charged quasiparticles always carry charges that are integer multiples of the electron charge.
Which of the statements given above are correctly stated?
- In the ν = 1/3 fractional quantum Hall state, the quasiparticles carry a charge of e/3.
- Anyons are excitations whose exchange can produce a phase different from ±1.
- Non-Abelian anyons have been proposed as a basis for fault-tolerant topological quantum computation.
- Fractionally charged quasiparticles always carry charges that are integer multiples of the electron charge.
- A. 1 and 3 only
- B. 2 and 4 only
- C. 1, 2 and 3 only
- D. 1, 3 and 4 only
Q10. The umbrella term 'quantum materials' groups together systems such as superconductors, topological insulators and strongly correlated electronic systems primarily on the basis of which one of the following organising concepts?
- A. Emergence of macroscopic properties from collective quantum effects
- B. Radioactive decay of constituent nuclei
- C. Classical ferromagnetic domain alignment
- D. Mechanical hardness exceeding that of diamond
Q11. Single-shot interferometric measurement of fermion parity in gate-defined InAs–Al superconducting devices — a milestone toward Majorana-based topological qubits — was reported in the journal Nature in which year?
- A. 2015
- B. 2019
- C. 2022
- D. 2025