In this Article
- The “quantum zoo” of strange matter has grown with the discovery of nearly a dozen new quantum states in twisted molybdenum ditelluride in Nature.
- These states, including magnet-free fractional quantum Hall effects, may support non-Abelian anyons, which are essential for topological quantum computers.
- Pump-probe spectroscopy, which detects small quantum state alterations with great sensitivity, revealed fractional charges and dynamic quantum behaviour.
The discovery and characterization of novel quantum states in twisted molybdenum ditelluride (tMoTe2) bilayers has advanced significantly in recent years, especially by members of Columbia University’s Energy Frontiers Research Centre (EFRC) on Programmable Quantum Materials (Pro-QM) and affiliated institutions. The known “quantum zoo” of exotic matter has been expanded with the discovery of approximately 20 hitherto undiscovered “hidden states” at fractional fills in tMoTe2, according to a recent study by Wang et al. published in Nature.
Magnet-free fractional quantum anomalous Hall (FQAH) states and possible candidates for theoretically predicted exotic topological phases, such as fractional topological insulators (FTI) and fractional quantum spin Hall (FQSH) states, are among the discoveries made possible by a highly sensitive pump-probe spectroscopy technique. Together with the discovery of states at fractional fills pertinent to non-Abelian anyons, the ability to produce these states without the need of an external magnetic field points to a possible avenue for the development of more stable, topological quantum computers.
Important Findings
New Quantum States Found and Described in Twisted MoTe2 Bilayers:
Twisted MoTe2 bilayers, a “Moiré material” made by twisting atom-thin layers of molybdenum ditelluride relative to one another, are the main subject of the study. A moiré pattern with special quantum characteristics is produced by this twisting.
Wang et al.’s study in Nature used transient optical spectroscopy, more precisely a pump-probe approach, to uncover over 20 “hidden states” in tMoTe2 that could not be found using transport measurements or static optical sensing. This method uses a probe pulse to detect melting and recovery dynamics after a pump pulse excites charge and disorder linked states.
A considerable number of states on the electron doping side (ν > 0), fractional fillings between v = 0 and -1, and crucially, new states at fractional fillings of the Chern bands at ν = -4/3, -3/2, -5/3, -7/3, -5/2, and -8/3 are among these recently discovered states.
The “quantum zoo” of known quantum states in materials is greatly increased by these discoveries. Some of these states have never been observed previously, according to Xiaoyang Zhu. We also didn’t anticipate seeing so many.
Unusual (magnet-free) Fractional Quantum Hall Effect Realization:
The study expands on the idea of the fractional quantum Hall effect (FQHE), which is the phenomena of quantised voltage fluctuations associated with fractional charges in two dimensions and at ultracold temperatures caused by interacting electrons. According to this theory, which shared a Nobel Prize with Horst Stormer, emergent particles with charges smaller than an individual electron can be produced by collective electron behaviour.
- The discovery of an anomalous (magnet-free) fractional quantum Hall effect (FQAH) in twisted MoTe2 layers by Xiaodong Xu in 2023 marked a significant advancement. Experiments conducted at Shanghai Jiao Tong University and Cornell University supported this.
- The topological characteristics brought about by the twisting of the MoTe2 layers are crucial to this magnet-free FQAH phenomenon. Since an external magnet can damage the superconducting materials used in modern quantum computers, this twisting produces an internal magnetic field instead.
Topological Quantum Computing Implications:
One important consequence of the recently found states is that they may host non-Abelian anyons, especially those at certain fractional fills. For topological quantum computers, these hypothetical particles are regarded as essential building ingredients.
Since the quantum information of topological quantum computers is encoded in the topological features of matter, they are resistant against local disturbances and theoretically more stable and error-prone than contemporary superconducting quantum computers.
A significant obstacle in the development of topological quantum computing is addressed by the capacity to produce the necessary topological states (such as FQAH states) without the use of an external magnetic field, as shown in tMoTe2.
High-Tech Experimental Methods:
Thanks to Eric Arsenault’s highly sensitive pump-probe spectroscopy technique, the “hidden states” were successfully identified.
With this method, quantum states are “melted” by an incredibly rapid laser, and as they recover, minute variations in the dielectric constant are detected. This makes it possible to probe minute variations in fractional energy levels.
According to Xiaoyang Zhu, this finding “establishes pump-probe spectroscopy as hitherto the most sensitive technique in detecting quantum states of matter.”
Correlated State Dynamics:
The discovery also sheds light on how the linked states in tMoTe2 behave. These states melt on two different time scales: 180-270 ps (ascribed to phonon mechanisms) and 2-4 ps (ascribed to electronic mechanisms).
Additionally discussed are the different dynamics of electron and hole doped states, which are probably caused by the different valence and moiré conduction bands.
We have “entered new dimension, time, to explore correlation and topology in the ground state,” according to Yiping Wang, and the materials “just keep surprising us, especially when we push them out of equilibrium.”
You can also read Spin Decoherence: How Quantum Systems Lose Information
Research Collaboration and Acknowledgement:
Researchers from the National Institute for Materials Science in Japan, Columbia University, and the University of Washington, many of whom are affiliated with the Pro-QM EFRC, collaborated on the study.
Its aim is “To discover, characterise, and deploy new forms of quantum matter controllable by gating, magnetic proximity and nano-mechanical manipulation.”
Pro-QM members Milan Delor and Raquel Queiroz were recently acknowledged as 2025 Sloan Research Fellows.
The scope of the center’s research is further illustrated by highlighting earlier work by Cory Dean, Andrew Millis, Abhay Pasupathy, and Jim Hone that discovered superconductivity in twisted semiconductor WSe2.
In summary:
The topic of programmable quantum materials has advanced significantly with the recent discovery of several “hidden states” in twisted MoTe2 bilayers with fractional fills. Together with the creation of a very sensitive detection method, the discovery of magnet-free fractional quantum anomalous Hall states and possible candidates for unusual topological phases offers up fascinating new directions for basic study of quantum matter. Importantly, these results offer a solid basis for the possible creation of topological quantum computers that manipulate non-Abelian anyons and are more reliable and resilient to errors. Further characterisation of these recently identified states and an investigation of their possible uses will be the main goals of future research.
You can also read Aquark Technologies Achieves Quantum Milestone Underwater
Sources:
- Excerpts from “Energy Frontiers Research Center | Physics, Chemistry and Engineering ; Energy Frontiers Research Center.” (Pro-QM EFRC Website)
- Excerpts from “Hidden states and dynamics of fractional fillings in twisted MoTe2 bilayers | Nature” (Wang et al., Nature, 2025)
- Excerpts from “Scientists Say New Species in Quantum Zoo Could Lead to Topological Quantum Computers” (Swayne, The Quantum Insider, 2025)