Split-gate cavity coupler for silicon circuit quantum electrodynamics

Borjans, Felix; Croot, Xanthe; Putz, Stefan; Mi, Xiao; Quinn, S. M.; Pan, Alan; Kerckhoff, Joseph; Pritchett, Emily; Jackson, Clayton A.; Edge, L. F.; Ross, Richard S.; Ladd, Thaddeus D.; Borselli, Matthew; Gyure, Mark F.; Petta, J. R.

doi:10.1063/5.0006442

Cited by 21 publications

(10 citation statements)

References 31 publications

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“…With 12 ≈ 0, the cavity response is the strongest around t 12 /h = 4 GHz (h is Planck's constant), where the energy difference of the coupled states is most insensitive to noise on the detuning axis 12 and the transition energy is resonant with the cavity E 2 − E 1 = hf c . In contrast to the valley-free case [48,51], here E 2 − E 1 < 2t 12 , as level repulsion from the excited valley states |1, + and |2, + reduce its effective energy splitting.…”

Section: Cavity Response To Valley Statesmentioning

confidence: 81%

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Probing the Spatial Variation of the Inter-Valley Tunnel Coupling in a Silicon Triple Quantum Dot

Borjans,

Zhang,

et al. 2021

Preprint

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Electrons confined in silicon quantum dots exhibit orbital, spin, and valley degrees of freedom. The valley degree of freedom originates from the bulk bandstructure of silicon, which has six degenerate electronic minima. The degeneracy can be lifted in silicon quantum wells due to strain and electronic confinement, but the "valley splitting" of the two lowest lying valleys is known to be sensitive to atomic-scale disorder. Large valley splittings are desirable to have a well-defined spin qubit. In addition, an understanding of the inter-valley tunnel coupling that couples different valleys in adjacent quantum dots is extremely important, as the resulting gaps in the energy level diagram may affect the fidelity of charge and spin transfer protocols in silicon quantum dot arrays. Here we use microwave spectroscopy to probe spatial variations in the valley splitting, and the intraand inter-valley tunnel couplings (tij and t ij ) that couple dots i and j in a triple quantum dot (TQD). We uncover large spatial variations in the ratio of inter-valley to intra-valley tunnel couplings t 12 /t12 = 0.90 and t 23 /t23 = 0.56. By tuning the interdot tunnel barrier we also show that t ij scales linearly with tij, as expected from theory. The results indicate strong interactions between different valley states on neighboring dots, which we attribute to local inhomogeneities in the silicon quantum well.

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Section: Cavity Response To Valley Statesmentioning

confidence: 81%

“…2(b). Along with screening gates S1 and S2, the CP gate is part of the first of three overlapping Al gate layers [51]. Plunger (barrier) gates are defined in the second (third) aluminum layers and the layers are electrically isolated from one another by a native Al 2 O 3 oxide barrier.…”

Section: Methodsmentioning

confidence: 99%

Probing the Spatial Variation of the Inter-Valley Tunnel Coupling in a Silicon Triple Quantum Dot

Borjans,

Zhang,

et al. 2021

Preprint

Self Cite

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“…The superconducting resonator has a galvanic connection to the gate S1 as a single layer variant of a split-gate coupler design which serves to decouple the cavity pin voltage from the neighboring quantum dot easing tuning constraints for two qubit samples. 39 Tuning the device as intended, a double quantum dot (DQD) can be formed and sensed under P1 and P2 using the TiN resonator as shown in Figure 3 (c). In the many electron regime the DQD has tunnel rates comparable to the resonator frequency resulting in a visible interdot transition shown in the inset of Figure 3…”

Section: Resultsmentioning

confidence: 99%

Dispersive measurement of a semiconductor double quantum dot via 3D integration of a high-impedance TiN resonator

Holman,

Rosenberg,

Yost

et al. 2020

Preprint

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Spins in semiconductor quantum dots are a candidate for cryogenic quantum processors due to their exceptionally long coherence times. One major challenge to scaling quantum dot spin qubits is the dense wiring requirements, making it difficult to envision fabricating large arrays of nearest-neighbor-coupled qubits necessary for error correction. We describe a method to solve this problem by spacing the qubits out using high-impedance superconducting resonators with a 2D grid unit cell area of 0.16 mm 2 using 3D integration. To prove the viability of this approach, we demonstrate 3D integration of a high-impedance TiN resonator coupled to a double quantum dot in a Si/SiGe heterostructure. Using the resonator as a dispersive gate sensor, we tune the device down to the single electron regime with an SNR = 5.36 limited by the resonator-dot capacitance. Characterization of the dot and resonator systems shows such integration can be done while maintaining low charge noise metrics for the quantum dots and with improved loaded quality factors for the superconducting resonator (Q L = 2.14 × 10 4 ), allowing for high-sensitivity charge detection and the potential for high fidelity 2-qubit gates. This work paves the way for 2D quantum dot qubit arrays with cavity mediated interactions.

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“…In this work, we study a triple quantum dot (TQD) coupled to a cavity via a split-gate cavity coupler [25]. By placing one quantum dot chemical potential on resonance with its neighboring lead, the cavity voltage excites resonant tunneling events, loading the cavity and reducing its quality factor and transmitted amplitude.…”

Section: Introductionmentioning

confidence: 99%

Spin digitizer for high-fidelity readout of a cavity-coupled silicon triple quantum dot

Borjans,

Mi,

Petta

2021

Preprint

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An important requirement for spin-based quantum information processing is reliable and fast readout of electron spin states, allowing for feedback and error correction. However, common readout techniques often require additional gate structures hindering device scaling or impose stringent constraints on the tuning configuration of the sensed quantum dots. Here, we operate an in-line charge sensor within a triple quantum dot, where one of the dots is coupled to a microwave cavity and used to readout the charge states of the other two dots. Owing to the proximity of the charge sensor, we observe a near-digital sensor response with a power signal-to-noise ratio >450 at an integration time of tint = 1 µs. Despite small singlet-triplet splittings ≈40 µeV, we further utilize the sensor to measure the spin relaxation time of a singlet-triplet qubit, achieving an average single-shot spin readout fidelity >99%. Our approach enables high-fidelity spin readout, combining minimal device overhead with flexible qubit operation in semiconductor quantum devices.

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Split-gate cavity coupler for silicon circuit quantum electrodynamics

Cited by 21 publications

References 31 publications

Probing the Spatial Variation of the Inter-Valley Tunnel Coupling in a Silicon Triple Quantum Dot

Probing the Spatial Variation of the Inter-Valley Tunnel Coupling in a Silicon Triple Quantum Dot

Dispersive measurement of a semiconductor double quantum dot via 3D integration of a high-impedance TiN resonator

Spin digitizer for high-fidelity readout of a cavity-coupled silicon triple quantum dot

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