Nature: Quantum Computing’s Reproducibility Crisis: Majorana Fermions
(Nature) Nature opens with: “The controversy over Majorana particles is eroding confidence in the field. More accountability and openness are needed — from authors, reviewers and journal editors.”
Sergey Frolov comments in his article following the opening about the recent retraction of publications claiming to have detected Majorana particles–retractions which were initiated by Frolov with colleague Vincent Mourik, a physicist at the University of New South Wales in Sydney, Australia. Frolov and Mourik raised concerns after obtaining additional data from the original experiments that were not included with the published paper.
A shadow has fallen over the race to detect a new type of quantum particle, the Majorana fermion, that could power quantum computers.
Frolov warns, “I’ve become concerned that, after a series of false starts, a significant fraction of the Majorana field is fooling itself. Several key experiments claiming to have detected Majorana particles, initially considered as breakthroughs, have not been confirmed.”
Experimentally, researchers are at loggerheads over whether Majoranas have been detected at all, let alone whether they’re an asset for quantum computing. As scepticism of the claims creeps beyond the cognoscenti, the field is at risk of getting a bad reputation, despite its untapped promise.
Producing Majoranas in the laboratory is very hard. Experiments combine cutting-edge fields such as nanotechnology, superconductivity, device engineering and materials science.
More than 100 groups have tried this. Two dozen have reported Majorana manifestations. These usually appear in the form of a characteristic electronic signal: a narrow peak in current as voltage is varied across the nanowire. Frolov was a member of one of the first teams to observe this, in 2012.
In 2020, these observations came under scrutiny after replication experiments were conducted. Science published an experiment led by researchers at Pennsylvania State University in University Park contradicting the 2017 report4. My group reproduced patterns from the 2018 Nature study, but demonstrated that they need not originate from Majorana. We did a cross-check on both ends of the same nanowire, but found a current peak on only one end. This violated the basic expectation from the theory that Majoranas always come in pairs. The rate of rebuttal is speeding up: researchers have not been able to confirm the findings6,7 of two separate papers claiming to have found Majorana regimes in nanowires.
The lesson: Majorana particles aren’t necessary to produce the current peak signals. Yet, affirmative papers kept coming out without even mentioning alternative explanations, creating the impression that a debate is raging between Majorana optimists and pessimists.