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Fast two-qubit logic with holes in germanium


Universal quantum information processing requires the execution of single-qubit and two-qubit logic. Across all qubit realizations1, spin qubits in quantum dots have great promise to become the central building block for quantum computation2. Excellent quantum dot control can be achieved in gallium arsenide3,4,5, and high-fidelity qubit rotations and two-qubit logic have been demonstrated in silicon6,7,8,9, but universal quantum logic implemented with local control has yet to be demonstrated. Here we make this step by combining all of these desirable aspects using hole quantum dots in germanium. Good control over tunnel coupling and detuning is obtained by exploiting quantum wells with very low disorder, enabling operation at the charge symmetry point for increased qubit performance. Spin–orbit coupling obviates the need for microscopic elements close to each qubit and enables rapid qubit control with driving frequencies exceeding 100 MHz. We demonstrate a fast universal quantum gate set composed of single-qubit gates with a fidelity of 99.3 per cent and a gate time of 20 nanoseconds, and two-qubit logic operations executed within 75 nanoseconds. Planar germanium has thus matured within a year from a material that can host quantum dots to a platform enabling two-qubit logic, positioning itself as an excellent material for use in quantum information applications.

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Fig. 1: Fabrication and operation of a planar germanium double quantum dot.
Fig. 2: Qubit control, gate fidelity and quantum coherence of planar germanium qubits.
Fig. 3: Tunable exchange coupling and operation at the charge symmetry point.
Fig. 4: Fast two-qubit logic with germanium qubits.

Data availability

All data underlying this study are available from the 4TU ResearchData repository at


  1. 1.

    Ladd, T. D. et al. Quantum computers. Nature 464, 45–53 (2010).

    ADS  Article  CAS  Google Scholar 

  2. 2.

    Loss, D. & DiVincenzo, D. P. Quantum computation with quantum dots. Phys. Rev. A 57, 120–126 (1998).

    ADS  Article  CAS  Google Scholar 

  3. 3.

    Hensgens, T. et al. Quantum simulation of a Fermi–Hubbard model using a semiconductor quantum dot array. Nature 548, 70–73 (2017).

    ADS  Article  CAS  Google Scholar 

  4. 4.

    Reed, M. et al. Reduced sensitivity to charge noise in semiconductor spin qubits via symmetric operation. Phys. Rev. Lett. 116, 110402 (2016).

    ADS  Article  CAS  Google Scholar 

  5. 5.

    Martins, F. et al. Noise suppression using symmetric exchange gates in spin qubits. Phys. Rev. Lett. 116, 116801 (2016).

    ADS  MathSciNet  Article  CAS  Google Scholar 

  6. 6.

    Veldhorst, M. et al. A two-qubit logic gate in silicon. Nature 526, 410–414 (2015).

    ADS  Article  CAS  Google Scholar 

  7. 7.

    Yoneda, J. et al. A quantum-dot spin qubit with coherence limited by charge noise and fidelity higher than 99.9%. Nat. Nanotechnol. 13, 102–106 (2017).

    ADS  Article  CAS  Google Scholar 

  8. 8.

    Huang, W. et al. Fidelity benchmarks for two-qubit gates in silicon. Nature 569, 532–536 (2019).

    ADS  Article  CAS  Google Scholar 

  9. 9.

    Zajac, D. M. et al. Resonantly driven CNOT gate for electron spins. Science 359, 439–442 (2018).

    ADS  MathSciNet  Article  CAS  Google Scholar 

  10. 10.

    Koppens, F. H. L. et al. Driven coherent oscillations of a single electron spin in a quantum dot. Nature 442, 766–771 (2006).

    ADS  Article  CAS  Google Scholar 

  11. 11.

    Petta, J. R. et al. Coherent manipulation of coupled electron spins in semiconductor quantum dots. Science 309, 2180–2184 (2005).

    ADS  Article  CAS  Google Scholar 

  12. 12.

    Foletti, S., Bluhm, H., Mahalu, D., Umansky, V. & Yacoby, A. Universal quantum control of two-electron spin quantum bits using dynamic nuclear polarization. Nat. Phys. 5, 903–908 (2009).

    Article  CAS  Google Scholar 

  13. 13.

    Veldhorst, M. et al. An addressable quantum dot qubit with fault-tolerant control-fidelity. Nat. Nanotechnol. 9, 981–985 (2014).

    ADS  Article  CAS  Google Scholar 

  14. 14.

    Bulaev, D. V. & Loss, D. Spin relaxation and decoherence of holes in quantum dots. Phys. Rev. Lett. 95, 076805 (2005).

    ADS  Article  CAS  Google Scholar 

  15. 15.

    Bulaev, D. V. & Loss, D. Electric dipole spin resonance for heavy holes in quantum dots. Phys. Rev. Lett. 98, 097202 (2007).

    ADS  Article  CAS  Google Scholar 

  16. 16.

    Maurand, R. et al. A CMOS silicon spin qubit. Nat. Commun. 7, 13575 (2016).

    ADS  Article  CAS  Google Scholar 

  17. 17.

    Watzinger, H. et al. A germanium hole spin qubit. Nat. Commun. 9, 3902 (2018).

    ADS  Article  CAS  Google Scholar 

  18. 18.

    Liles, S. D. et al. Spin and orbital structure of the first six holes in a silicon metal-oxide-semiconductor quantum dot. Nat. Commun. 9, 3255 (2018).

    ADS  Article  CAS  Google Scholar 

  19. 19.

    Hu, Y., Kuemmeth, F., Lieber, C. M. & Marcus, C. M. Hole spin relaxation in Ge–Si core–shell nanowire qubits. Nat. Nanotechnol. 7, 47–50 (2012).

    ADS  Article  CAS  Google Scholar 

  20. 20.

    Vukušić, L. et al. Single-shot readout of hole spins in Ge. Nano Lett. 18, 7141–7145 (2018).

    ADS  Article  CAS  Google Scholar 

  21. 21.

    Dobbie, A. et al. Ultra-high hole mobility exceeding one million in a strained germanium quantum well. Appl. Phys. Lett. 101, 172108 (2012).

    ADS  Article  CAS  Google Scholar 

  22. 22.

    Hendrickx, N. W. et al. Gate-controlled quantum dots and superconductivity in planar germanium. Nat. Commun. 9, 2835 (2018).

    ADS  Article  CAS  Google Scholar 

  23. 23.

    Sammak, A. et al. Shallow and undoped germanium quantum wells: a playground for spin and hybrid quantum technology. Adv. Funct. Mater. 29, 1807613 (2019).

    Article  CAS  Google Scholar 

  24. 24.

    Lodari, M. et al. Light effective hole mass in undoped Ge/SiGe quantum wells. Phys. Rev. B 100, 041304 (2019).

    ADS  Article  CAS  Google Scholar 

  25. 25.

    Nenashev, A. V., Dvurechenskii, A. V. & Zinovieva, A. F. Wave functions and g factor of holes in Ge/Si quantum dots. Phys. Rev. B 67, 205301 (2003).

    ADS  Article  CAS  Google Scholar 

  26. 26.

    Maier, F., Kloeffel, C. & Loss, D. Tunable g factor and phonon-mediated hole spin relaxation in Ge/Si nanowire quantum dots. Phys. Rev. B 87, 161305 (2013).

    ADS  Article  CAS  Google Scholar 

  27. 27.

    Knill, E. et al. Randomized benchmarking of quantum gates. Phys. Rev. A 77, 012307 (2008).

    ADS  Article  CAS  Google Scholar 

  28. 28.

    Hutin, L. et al. in 2018 48th European Solid-State Device Research Conference (ESSDERC), 12–17 (2018).

  29. 29.

    Malinowski, F. K. et al. Notch filtering the nuclear environment of a spin qubit. Nat. Nanotechnol. 12, 16–20 (2017).

    ADS  Article  CAS  Google Scholar 

  30. 30.

    Itoh, K. M. & Watanabe, H. Isotope engineering of silicon and diamond for quantum computing and sensing applications. MRS Commun. 4, 143–157 (2014).

    Article  CAS  Google Scholar 

  31. 31.

    Russ, M. et al. High-fidelity quantum gates in Si/SiGe double quantum dots. Phys. Rev. B 97, 085421 (2018).

    ADS  Article  CAS  Google Scholar 

  32. 32.

    Vandersypen, L. M. K. & Chuang, I. L. NMR techniques for quantum control and computation. Rev. Mod. Phys. 76, 1037–1069 (2005).

    ADS  Article  Google Scholar 

  33. 33.

    Takeda, K. et al. Optimized electrical control of a Si/SiGe spin qubit in the presence of an induced frequency shift. npj Quantum Inf. 4, 54 (2018).

    ADS  Article  Google Scholar 

  34. 34.

    He, L., Bester, G. & Zunger, A. Electronic phase diagrams of carriers in self-assembled quantum dots: violation of Hund’s rule and the Aufbau principle for holes. Phys. Rev. Lett. 95, 246804 (2005).

    ADS  Article  CAS  Google Scholar 

  35. 35.

    Reuter, D. et al. Coulomb-interaction-induced incomplete shell filling in the hole system of InAs quantum dots. Phys. Rev. Lett. 94, 026808 (2005).

    ADS  Article  CAS  Google Scholar 

  36. 36.

    Hensen, B. et al. A silicon quantum-dot-coupled nuclear spin qubit. Nat. Nanotechnol. Preprint at (2019).

  37. 37.

    Crippa, A. et al. Electrical spin driving by g-matrix modulation in spin-orbit qubits. Phys. Rev. Lett. 120, 137702 (2018).

    ADS  Article  CAS  Google Scholar 

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We thank L. M. K. Vandersypen, S. Dobrovitski and J. Helsen for valuable discussions. We acknowledge support through a FOM Projectruimte of the Foundation for Fundamental Research on Matter (FOM), associated with the Netherlands Organisation for Scientific Research (NWO).

Author information




N.W.H. and D.P.F. performed the experiments. N.W.H. fabricated the device. A.S. and G.S. supplied the heterostructures. N.W.H., D.P.F. and M.V. wrote the manuscript with the input of all other authors. M.V. conceived and supervised the project.

Corresponding author

Correspondence to M. Veldhorst.

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Extended data figures and tables

Extended Data Fig. 1 Instrumentation set-up for the lock-in transport measurements.

Illustration of the set-up and relevant signals for the lock-in transport measurements. The AWG is used to generate alternating pulse cycles consisting of a repeated measurement and a repeated reference. The signal is demodulated in a lock-in amplifier to give a direct measure of the difference between the two measurements and subtract slow variations in the transport signal.

Extended Data Fig. 2 Pulse cycles used for the transport measurements.

a Pulse cycles used for the randomized benchmarking experiments. The measurement pulse cycle consists of m gates randomly drawn from the Clifford group Crand and a final Clifford gate projecting the qubit onto the spin-up state. The reference pulse cycle consists of the same m Clifford gates and a different final Clifford gate projecting the qubit onto the spin-down state. Each cycle is repeated N times, and a series of typically k = 50 independent randomly drawn measurement and reference pulse cycles are alternated. These k = 50 different draws are thus hardware-averaged on the lock-in amplifier, and the entire experiment is repeated and averaged 30 times, yielding a total approximate 105 repetitions of 1,500 different randomly drawn Clifford sequences of length m. An example of the qubit evolution for each pulse cycle is plotted on the Bloch sphere below. b, Pulse cycles used for the exchange mapping experiments. The measurement pulse cycle consists of a broad preparation and restoring pulse at frequency f3 (f1), around a probing pulse at frequency fprb. The reference pulse cycle consists solely of the probing pulse at fprb. The qubit evolutions for the different resonance conditions are plotted on the Bloch sphere and illustrate the different signals measured in Fig. 4c, d.

Extended Data Fig. 3 Demonstration of qubit operation at a second hole occupancy.

a, Charge stability diagram showing the (m, n) hole occupancy used during all experiments in the main text, as well as the (m, n + 1) occupancy for which we observe PSB as well. For an unpolarized filling of the quantum dots, one expects an alternating suppression of the transport current due to PSB, as spin blockade occurs only when an orbital level is fully occupied. However, the spin-filling for holes is known to be highly polarized34,35, and therefore PSB can occur in sequential quantum dot fillings. b, Coherent Rabi oscillations measured in the (m, n + 1) occupancy. A slight linear offset is observed for Q1, which can be attributed to the microwave power. We note that, for the same microwave power, the Rabi frequency of Q2 in the (m, n + 1) occupancy is increased substantially compared to the (m, n) filling. We attribute this to the hole being in a different orbital, where the effective SOC may be different.

Extended Data Fig. 4 Qubit resonance frequencies as a function of magnetic field.

Colour plot indicating the transport current ΔI through the double dot system, as a function of external magnetic field B0 and the frequency f of the applied microwave signal. We have numerically subtracted the mean of each row and column in each of the three individual colour plots, to account for the slow drifts in transport current, as well as the line resonances in our fridge cabling. The two bright lines indicate an increase in the transport current due to the microwave rotating either spin and thus lifting PSB.

Extended Data Fig. 5 Temporal dependence of the resonance frequency.

We track the resonance frequency of both Q1 and Q2 over the time of approximately 110 h. We observe that the qubit frequency remains remarkably stable over this period, but do observe discrete, uncorrelated steps in the resonance frequencies of both qubits. The resonance frequency of Q1 only shows steps of Δf ≈ 2 MHz between two distinct levels, whereas for Q2 we observe steps of both Δf ≈ 1 MHz and Δf ≈ 2 MHz, between three different levels, as also becomes apparent from the histogram. The origin of these steps could be, for example, the slow loading and unloading of charge traps, which manipulates the qubit resonance frequency through the change in electric field, or hyperfine coupling to a nearby nuclear spin36.

Extended Data Fig. 6 Magnetic field dependence of the driving speed of Q1.

a, b, Rabi frequency dependence on the applied microwave power P in arbitrary units, for B0 = 0.5 T (a) and B0 = 1.65 T (b). Multiple mechanisms can be at play for the EDSR driving of the spins37 and these are typically all linearly dependent on B0. As a result of this, considerably higher driving frequencies can be reached at higher magnetic fields. We note that the exact microwave power cannot be compared between the two measurements, owing to the strong frequency dependence of the attenuation of our fridge lines.

Extended Data Fig. 7 Relaxation, dephasing and coherence times.

We perform a Ramsey experiment, in which two π/2 pulses are separated by time τ, during which the qubit will evolve as a result of the implemented detuning. We fit the decay of the observed oscillations to \(\Delta {I}_{{\rm{S}}{\rm{D}}}=a\cos (2{\rm{\pi }}\Delta f\tau +\varphi )\exp [-{(\tau /{T}_{2}^{* })}^{\alpha * }]\), with a a scaling factor, Δf the detuning and ϕ a phase offset, and find a spin coherence time of \({T}_{2,{\rm{Q}}1}^{* }=833\,{\rm{n}}{\rm{s}}\) and \({T}_{2,{\rm{Q}}2}^{* }=419\,{\rm{n}}{\rm{s}}\) and decay coefficients of \({\alpha }_{{\rm{Q}}1}^{* }=1.2\pm 0.2\) and \({\alpha }_{{\rm{Q}}2}^{* }=1.5\pm 0.2\), for Q1 and Q2, respectively. The spin coherence can be extended by performing a Hahn echoing sequence, consisting of π/2, π and π/2 pulses separated by waiting times τ. Fitting the observed decay as a function of the total waiting time 2τ to a power law \(\Delta {I}_{{\rm{S}}{\rm{D}}}=a\exp [-{(2\tau /{T}_{2}^{* })}^{{\alpha }^{{\rm{H}}}}]\), we find extended coherence times of \({T}_{2,{\rm{Q}}1}^{{\rm{H}}}=1.9\,\mu {\rm{s}}\) and \({T}_{2,{\rm{Q}}2}^{{\rm{H}}}=0.8\,\mu {\rm{s}}\) and decay coefficients of \({\alpha }_{{\rm{Q1}}}^{{\rm{H}}}=1.5\pm 0.1\) and \({\alpha }_{{\rm{Q2}}}^{{\rm{H}}}=2.5\pm 0.3\), for Q1 and Q2, respectively. Finally, we perform a measurement of the spin lifetime by applying a single π pulse, after which we wait for a time τ. We fit the decay to \(\Delta {I}_{{\rm{S}}{\rm{D}}}=\exp [-(\tau /{T}_{1})]\) and find lifetimes of T1,Q1 = 9 μs and T1,Q2 = 3 μs.

Extended Data Fig. 8 Relaxation time T1 as a function of gate voltage on the tunnel barriers between dot and reservoir.

a, b, The relaxation time T1 of the dots increases approximately exponentially as a function of the respective dot–reservoir gate voltage, for Q1 (a) as well as for Q2 (b). The relaxation time of Q1 increases exponentially from T1 < 1 μs to T1 > 10 μs, and a similar scaling is observed for Q2. For even smaller dot–reservoir couplings, the transport signal drops below our measurement limit, but switching to charge sensing could allow a further increase in T1.

Extended Data Fig. 9 Phase corrections on the qubits.

a, Extended Ramsey experiment on each of the four resonance line, using five different test gates between the π/2 pulses to observe the effect on the resonance frequency. A linear phase shift as a function of test gate pulse length τ can be observed for some lines, indicating a frequency shift during the pulsing. b, We compensate for this effect by performing a software update of δϕ = δντ to each additional pulse, with δν the frequency shift of the qubit as a result of the microwave signal.

Supplementary information

Video 1

Videomode operation of the tuning of the dot-reservoir coupling (Q1-S).

Video 2

Videomode operation of the tuning of the dot-reservoir coupling (Q2-D).

Video 3

Videomode operation of the tuning of the dot-dot coupling (Q1-Q2).

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Hendrickx, N., Franke, D., Sammak, A. et al. Fast two-qubit logic with holes in germanium. Nature 577, 487–491 (2020).

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