“…MHz while the maximum driving strength is set to Ω max = 10 MHz such that they are of similar strength and the rotating wave approximation is certainly invalid. Currently, driving strengths of MHz have been implemented in experiments [2,5,[30][31][32][33]. The maximum exchange strength was chosen to be J max = 10 MHz, which is readily attainable in experiments [34].…”
Spin qubits in semiconductor quantum dots are a promising platform for quantum computing,
however, scaling to large systems is hampered by crosstalk and charge noise. Crosstalk here refers
to the unwanted off-resonant rotation of idle qubits during the resonant rotation of the target qubit.
For a three-qubit system with crosstalk and charge noise, it is difficult to analytically create gate
protocols that produce three-qubit gates, such as the Toffoli gate, directly in a single shot instead of
through the composition of two-qubit gates. Therefore, we numerically optimize a physics-informed
neural network to produce theoretically robust shaped pulses that generate a Toffoli-equivalent gate.
Additionally, robust π/2 X and cz gates are also presented in this work to create a universal set of
gates robust against charge noise. The robust pulses maintain an infidelity of 10−3 for average
quasistatic fluctuations in the voltage of up to a few mV instead of tenths of mV for non-robust
pulses.
“…MHz while the maximum driving strength is set to Ω max = 10 MHz such that they are of similar strength and the rotating wave approximation is certainly invalid. Currently, driving strengths of MHz have been implemented in experiments [2,5,[30][31][32][33]. The maximum exchange strength was chosen to be J max = 10 MHz, which is readily attainable in experiments [34].…”
Spin qubits in semiconductor quantum dots are a promising platform for quantum computing,
however, scaling to large systems is hampered by crosstalk and charge noise. Crosstalk here refers
to the unwanted off-resonant rotation of idle qubits during the resonant rotation of the target qubit.
For a three-qubit system with crosstalk and charge noise, it is difficult to analytically create gate
protocols that produce three-qubit gates, such as the Toffoli gate, directly in a single shot instead of
through the composition of two-qubit gates. Therefore, we numerically optimize a physics-informed
neural network to produce theoretically robust shaped pulses that generate a Toffoli-equivalent gate.
Additionally, robust π/2 X and cz gates are also presented in this work to create a universal set of
gates robust against charge noise. The robust pulses maintain an infidelity of 10−3 for average
quasistatic fluctuations in the voltage of up to a few mV instead of tenths of mV for non-robust
pulses.
“…In order to enhance the strength of EDSR and SPI, much effort has been devoted to exploring the use of a double quantum dot (DQD) instead of a single dot [ 96 ] and brought the excited states closer to the qubit states, [ 97 ] both of which can produce a larger electric dipole moment. Thus, by carefully considering these factors, we can work toward developing even more powerful and scalable semiconductor quantum computing schemes.…”
Section: Microscopic Physics Of Semiconductor Nanostructuresmentioning
Quantum computing offers the potential to revolutionize information processing by exploiting the principles of quantum mechanics. Among the diverse quantum bit (qubit) technologies, silicon‐based semiconductor spin qubits have emerged as a promising contender due to their potential scalability and compatibility with existing semiconductor technologies. In this paper, the latest developments of spin qubits in gate‐defined semiconducting nanostructures made of silicon and germanium, starting from the basic properties of electron and hole states in group‐IV semiconductors, are reviewed. Specifically, various nanostructures that exploit their unique microscopic properties for qubit implementations, elaborating on the advances and challenges in experiments, are discussed. Strategies for enhancing qubit performance, such as designing new nanostructures and identifying suitable operating points, particularly those involving the valleys of electron qubits and the heavy‐hole–light‐hole mixing of hole qubits, are also highlighted. This comprehensive review thus provides valuable insights into the current state‐of‐the‐art in semiconductor quantum computing and suggests avenues for future research.
“…Foremost among these challenges is scalability, whereby large numbers of addressable quantum bits, or qubits, can be integrated into complex circuitry capable of implementing useful quantum algorithms with embedded quantum error correction. 5,6 Among the many qubit platforms under consideration 7 (e.g., solid state defects, 8 quantum dots, 9 photons, 3 trapped atoms/ions, 10,11 and superconducting circuits 4,12 ), electron and nuclear spins in molecules are gaining interest. 13−15 Molecular spins possess discrete energy levels, while the associated quantum states can be tuned and coherently manipulated using external electromagnetic fields.…”
Section: Introductionmentioning
confidence: 99%
“…The superiority of quantum computers for performing certain computational tasks has been well established at the theoretical level, , while practical devices are getting ever closer to attaining quantum advantage. , However, many challenges remain before the full potential of quantum information science can be unleashed. Foremost among these challenges is scalability, whereby large numbers of addressable quantum bits, or qubits, can be integrated into complex circuitry capable of implementing useful quantum algorithms with embedded quantum error correction. , Among the many qubit platforms under consideration (e.g., solid state defects, quantum dots, photons, trapped atoms/ions, , and superconducting circuits , ), electron and nuclear spins in molecules are gaining interest. − Molecular spins possess discrete energy levels, while the associated quantum states can be tuned and coherently manipulated using external electromagnetic fields. , Crucially, chemistry-inspired supramolecular or self-assembly approaches are well-suited to tackling the issue of scalability. − …”
Molecular lanthanide (Ln) complexes are promising candidates for the development of next-generation quantum technologies. High-symmetry structures incorporating integer spin Ln ions can give rise to well-isolated crystal field quasi-doublet ground states, i.e., quantum two-level systems that may serve as the basis for magnetic qubits. Recent work has shown that symmetry lowering of the coordination environment around the Ln ion can produce an avoided crossing or clock transition within the ground doublet, leading to significantly enhanced coherence. Here, we employ single-crystal high-frequency electron paramagnetic resonance spectroscopy and high-level ab initio calculations to carry out a detailed investigation of the nine-coordinate complexes, [Ho III L 1 L 2 ], where L 1 = 1,4,7,10-tetrakis(2-pyridylmethyl)-1,4,7,10-tetraaza-cyclododecane and L 2 = F − (1) or [MeCN] 0 (2). The pseudo-4-fold symmetry imposed by the neutral organic ligand scaffold (L 1 ) and the apical anionic fluoride ion generates a strong axial anisotropy with an m J = ±8 ground-state quasi-doublet in 1, where m J denotes the projection of the J = 8 spin−orbital moment onto the ∼C 4 axis. Meanwhile, off-diagonal crystal field interactions give rise to a giant 116.4 ± 1.0 GHz clock transition within this doublet. We then demonstrate targeted crystal field engineering of the clock transition by replacing F − with neutral MeCN (2), resulting in an increase in the clock transition frequency by a factor of 2.2. The experimental results are in broad agreement with quantum chemical calculations. This tunability is highly desirable because decoherence caused by second-order sensitivity to magnetic noise scales inversely with the clock transition frequency.
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