2022, what a year it has been! As the research in quantum computing continues to increase its pace, we take it upon ourselves to consistently support this growth by providing state-of-the-art hardware and software for quantum control as well as advanced quantum electronics.
Given this commitment, we at QM are proud to share the incredible research that our customers have published over the past year facilitated by QM’s Quantum Orchestration ®. So let’s dive in and take a look at our 2022 year-in-review list of research works.
Quantum Zeno w/o Interacting Qubits
Demonstration of universal control between non-interacting qubits using the Quantum Zeno effect
On the boundary between coherence and incoherent control lies the Quantum Zeno effect. The work of Blumenthal et al. is the first experimental demonstration of its use to obtain universality without interacting qubits, showing single-qubit operations turning into a multi-qubit entangling gate. Carefully engineered and calibrated Zeno drive effectively freezes the dynamics of the system from the Hilbert space to a subsection with distinct eigenvalues of the measured observable. Within this subspace, control is fully coherent. Learn more here.
Multi-Qubit Dark States
Coherent control of a multi-qubit dark state in waveguide quantum electrodynamics
There has always been a tension between the ability to control qubits efficiently, which implies some coupling to the environment against the need for long coherence times, which instead require very isolated systems. In the work of Zanner et al., the authors show coherent control of a dark state composed of four qubits coupled via a waveguide. Utilizing the symmetry properties of the collective state manifold, they designed a control mechanism that overcomes the limitations of dark states, notoriously difficult to drive but showcasing much longer coherence than their bright counterpart. This experiment paves the way for the utilization of decoherence-free subspaces for quantum information technologies. Learn more here.
Nanoscale electric field imaging with an ambient scanning quantum sensor microscope
While incredible demonstrations exist in the literature regarding the use of NV centers for magnetometry, NV electrometry demonstrations have been lacking. In their recent work, Qiu et al. have demonstrated AC and DC electrical field sensing and imaging using an NV center placed on a diamond scanning tip. They used an XY-4 lock-in procedure, obtaining a Ramsey phase signal that depends on the external electric field detected. Thanks to an oscillatory motion applied to the scanning tip in synchronization with the OPX+ pulse sequences, the team measured even DC electric fields, resulting in astonishing maps of the electric fields applied to their gold structure, with sub-100nm resolution. Learn more here.
Silicon Spin Qubits Above Fault-Tolerance Threshold
Fast universal quantum gate above the fault-tolerance threshold in silicon
With the incredible work from Noiri et al., Silicon spin qubits achieve 99.5% two-qubit gate fidelity and 99.8% single-qubit gate fidelity, surpassing the 99% error correction threshold required for fault-tolerant quantum computers. Based on this setup, the authors realized Deutsch–Jozsa and Grover search algorithms with high success rates. The above-threshold operation could lead to scalable quantum computers using silicon technology. Learn more here.
Topological Control via Spin-Orbit coupling
Spin-orbit–driven ferromagnetism at half moiré filling in magic-angle twisted bilayer graphene
By examining a two-dimensional system at the atomic interface between twisted bilayer graphene and a tungsten diselenide crystal, Lin et al. found that strong electron correlation within the moiré flatband stabilizes correlated insulating states and that spin-orbit coupling transforms these insulators into ferromagnets, as evidenced by a robust anomalous Hall effect. The coupling between spin and valley degrees of freedom can be controlled using an in-plane magnetic field or a perpendicular electric field, providing a way to engineer the topological properties of moiré bands in twisted bilayer graphene and related systems. Learn more here.
Silicon Quantum Dots: Autonomous Estimation of Coulomb Diamonds
Autonomous Estimation of High-Dimensional Coulomb Diamonds from Sparse Measurements
Chatterjee et al. developed and demonstrated a hardware-triggered detection method using reflectometry and a learning algorithm to map the ground states of few-dot quantum dot arrays, which are used as spin qubits in quantum processors. The method allows for the acquisition of measurements corresponding to transitions between ground states and was successfully demonstrated in a 2x2 array of silicon quantum dots, showcasing a vastly more practical characterization protocol than what was previously used. Learn more here.
Spin Qubits in Silicon Quantum Dots: Linking Distant Quantum Processors
A shuttling-based two-qubit logic gate for linking distant silicon quantum processors
In the recent work from Noiri et al., the authors demonstrated a two-qubit gate between spin qubits in silicon quantum dots using coherent spin shuttling, enabling the exchange coupling to be efficiently switched on and off while preserving spin coherence. This technology is crucial for linking distant silicon quantum processors, a key requirement for large-scale quantum computation. The technique was used to successfully demonstrate a two-qubit controlled-phase gate with a fidelity of 93%. Learn more here.
JDE in topological semimetal
Josephson diode effect from Cooper pair momentum in a topological semimetal
In the recent work from Pal et al., the authors showcase a giant Josephson diode effect in Josephson junctions made from a type-II Dirac semimetal, NiTe2. They found that the asymmetry in the critical current depends on the magnitude and direction of an applied magnetic field, reaching its maximum when the field is perpendicular to the current and is just 10 mT. The asymmetry also changes sign multiple times with an increasing field. The findings could lead to the development of new superconducting computing devices using the Josephson diode effect. Learn more here.
Understanding Graphene Superconductivity
Isospin order in superconducting magic-angle twisted trilayer graphene
Liu et al. have integrated magic-angle twisted trilayer graphene into a double-layer structure to study the superconducting phase. The authors found that Coulomb repulsion competes with the mechanism underlying Cooper pairing and used a combination of transport and thermodynamic measurements to probe the ground-state order, which suggests a spin-polarized and valley-unpolarized configuration at half moiré filling and for the Fermi surface at doping levels close to that point. These findings could help to better understand the nature of superconductivity in magic-angle twisted trilayer graphene. Learn more here.
A huge number of other works by our customers has been released in pre-print while awaiting peer review. Let’s have a peek at a few of them.
Superconducting Qubits Pre-Prints
A scalable superconducting quantum simulator with long-range connectivity based on a photonic bandgap metamaterial. Zhang et al., arXiv preprint arXiv:2206.12803 (2022).
The authors demonstrate simultaneous active reset on 10 qubits leveraging the real-time capabilities of the OPX+. They show how real-time control flow allows for subsequent initializations to increase the chance of getting to a fully initialized system. Read it here.
A quantum Szilard engine for two-level systems coupled to a qubit. Spiecker et al., arXiv preprint arXiv:2204.00499 (2022).
A superconducting fluxonium qubit gets coupled to a two-level system that mimics an environment of unknown origin. The authors show that real-time control flow capabilities (enabled by OPX+) allow for the stabilization and control of heat transfer between the two systems. Read it here.
Mitigation of quasiparticle loss in superconducting qubits by phonon scattering. Bargerbos et al., arXiv preprint arXiv:2207.12754 (2022).
Bargerbos et al. demonstrated a technique for mitigating the effect of ionizing radiation on superconducting qubits. Such radiation can create correlated errors which violate the requirements of error correction schemes, but proper shielding can reduce its effect. Read it here.
Direct manipulation of a superconducting spin qubit strongly coupled to a transmon qubit. Pita-Vidal et al., arXiv preprint arXiv:2208.10094 (2022).
Demonstration and manipulation of an Andreev spin qubit offer a new set of advantages over traditional spin platforms. Pita-Vidal et al. not only demonstrated Andreev spin qubit operation but embedded it in a transmon qubit, setting the stage for a hybrid architecture. Read it here.
Schrodinger cat states of a 16-microgram mechanical oscillator. Bild et al., arXiv preprint arXiv:2211.00449 (2022).
The boundary between classical and quantum worlds got very thin thanks to the work of Bild et al., which demonstrated a cat state on a macroscopic mechanical oscillator living in a superposition of oscillations with opposite phases. Read it here.
Cloaking a qubit in a cavity. Lledó et al., arXiv preprint arXiv:2211.05758 (2022).
Lledó et al. demonstrated the decoupling of a qubit from the photon population of the cavity which holds it. This is done by actively driving the qubit with a tone that destructively interferes with the cavity field, effectively leaving the qubit in a seemingly empty cavity. Read it here.
Demonstration of Quantum Advantage in Microwave Quantum Radar. Assouly et al., arXiv preprint arXiv:2211.05684 (2022).
Quantum advantage does not only apply to computing, as demonstrated by Assouly et al., which showed an advantage in a quantum radar, where entangled probe and idler are recombined and measured to evidence the presence of a target. Read it here.
Resolving non-perturbative renormalization of a microwave-dressed weakly anharmonic superconducting qubit. Ann et al., arXiv preprint arXiv:2212.05847 (2022).
Ann et al. investigate a microwave-dressed transmon in a wide range of parameters and establish a concise theory beyond the two-state model that represents its dynamics. Read it here.
Spins and Defect Centers Pre-Prints
On-demand electrical control of spin qubits. Gilbert et al., arXiv preprint arXiv:2201.06679 (2022).
The team demonstrated an on-demand interaction between the spin and orbital motion of electrons in silicon quantum dots. They could get long coherence, fast gates, and very high gate fidelity demonstrated by randomized benchmarking with depth 10000. Read it here.
Real-time frequency estimation of a qubit without single-shot-readout. Zohar et al., arXiv preprint arXiv:2210.05542 (2022).
Zohar et al. leveraged the real-time capabilities of the OPX+ to implement a phase estimation algorithm on an NV center used as a sensor, demonstrating improved sensitivity from the binomial distribution approach versus majority voting. Read it here.
Photonics and More
One hundred second bit-flip time in a two-photon dissipative oscillator. Berdou et al., arXiv preprint arXiv:2204.09128 (2022).
A 100s bit-flip time effectively means having a bit-flip-protected state. The authors show such a timescale in a Josephson circuit designed to circumvent all the suspected sources of instability. Read it here.
A quantum electromechanical interface for long-lived phonons. Bozkurt et al., arXiv preprint arXiv:2207.10972 (2022).
A demonstration of mechanical lifetimes of over 200us for low-phonon numbers and millikelvin temperatures has been shown by Bozkurt et al. Ground state operation, long lifetimes, and strong coupling set the stage for electromechanical oscillators to use as memory and transducers. Read it here.
Optically heralded microwave photons. Jiang et al., arXiv preprint arXiv:2210.10739 (2022).
Jiang et al. demonstrated entanglement between microwave and optical photons, a transducer technology based on gigahertz nanomechanical resonances. Further work could lead to a scalable network between distant quantum processors based on superconducting qubits. Read it here.
Electron charge qubits on solid neon with 0.1 millisecond coherence time. Zhou et al., arXiv preprint arXiv:2210.12337 (2022).
Electron charge qubits are back with elongated coherence times thanks to a unique platform developed by Zhou et al., which reduces charge noise in the host material, the primary source of decoherence, making electron charge qubits a viable alternative for quantum computing. Read it here.
2022 really has been an incredible year. As we push further toward the realization of practical quantum computers, there is no better feeling than watching such incredible research being published and observing what quantum experimentalists can do. We look forward to what is to come! Stay tuned for 2023!
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