A fast quantum interface between different spin qubit encodings

Noiri, Akito; Nakajima, Takashi; Yoneda, Jun; Delbecq, Matthieu; Stano, Peter; Otsuka, Takeshi; Takeda, Kenta; Amaha, S.; Allison, Giles; Kawasaki, Kento; Kojima, Y.; Ludwig, Arne; Wieck, A. D.; Loss, Daniel; Tarucha, Seigo

doi:10.1038/s41467-018-07522-1

Cited by 31 publications

(28 citation statements)

References 36 publications

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“…1). This effect is expected to be suppressed by further quenching the residual exchange coupling (~MHz), e.g., via an interdot gate electrode 6 or by fast readout with an ancilla encoded in double-dot spin states 22 . We anticipate that we will then improve F QND and the QND readout in all aspects, as a higher F QND should raise F M and F P that are achievable by repeating QND measurements.…”

Section: Discussionmentioning

confidence: 99%

Quantum non-demolition readout of an electron spin in silicon

et al. 2020

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While single-shot detection of silicon spin qubits is now a laboratory routine, the need for quantum error correction in a large-scale quantum computing device demands a quantum non-demolition (QND) implementation. Unlike conventional counterparts, the QND spin readout imposes minimal disturbance to the probed spin polarization and can therefore be repeated to extinguish measurement errors. Here, we show that an electron spin qubit in silicon can be measured in a highly non-demolition manner by probing another electron spin in a neighboring dot Ising-coupled to the qubit spin. The high non-demolition fidelity (99% on average) enables over 20 readout repetitions of a single spin state, yielding an overall average measurement fidelity of up to 95% within 1.2 ms. We further demonstrate that our repetitive QND readout protocol can realize heralded high-fidelity (>99.6%) groundstate preparation. Our QND-based measurement and preparation, mediated by a second qubit of the same kind, will allow for a wide class of quantum information protocols with electron spins in silicon without compromising the architectural homogeneity.

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Section: Discussionmentioning

confidence: 99%

Quantum non-demolition readout of an electron spin in silicon

et al. 2020

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“…Furthermore, we demonstrate the detection of coherent operation of two individual ST 0 qubits in a quadruple QD array with a single rfreflectometry line. We stress that we combine previous methods, which individually demonstrated the Elzerman readout of the twoelectron spin states 12 , large ΔB // generation with micromagnet 33 , high-fidelity control of the ST 0 qubit 36 , and robust measurement within a single quantum processor yielding a record high quantum oscillation visibility in large ΔB // . We also note that this Green panel: At the PSB readout point, the (1,1)S state tunnels into the (2,0) charge state while the tunneling from the (1,1)T 0 state is blocked.…”

Section: Introductionmentioning

confidence: 92%

“…1b). A 250-nm thick rectangular Co micromagnet with large shape anisotropy was deposited on top of the heterostructure to generate stable ΔB // for ST 0 qubit operation 33,36,39,40 (see methods section for fabrication details). The device was placed on a plate in a dilution refrigerator at~20 mK and an in-plane magnetic field B z,ext of 225 mT was applied.…”

Section: Energy-selective Tunneling Readoutmentioning

confidence: 99%

“…In this work, we focused on independent two single-qubit gate operation; nevertheless, we expect that long T 1 at EST readout will allow the sequential measurement of two-qubit states for a given quantum operation, which, in turn, will allow two-qubit correlation measurement, enabling full two-qubit state and process tomography in the future. Characterization of the two-qubit interaction of ST 0 qubits in the current quadruple dot array, for example by dipole coupling 6,10 or exchange interaction 36 , is the subject of current investigations.…”

Section: High-visibility Quantum Control With the Est Readoutmentioning

confidence: 99%

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Robust energy-selective tunneling readout of singlet-triplet qubits under large magnetic field gradient

et al. 2020

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Fast and high-fidelity quantum state detection is essential for building robust spin-based quantum information processing platforms in semiconductors. The Pauli spin blockade (PSB)-based spin-to-charge conversion and its variants are widely used for the spin state discrimination of two-electron singlet-triplet (ST 0) qubits; however, the single-shot measurement fidelity is limited by either the low signal contrast, or the short lifetime of the triplet state at the PSB energy detuning, especially due to strong mixing with singlet states at large magnetic field gradients. Ultimately, the limited single-shot measurement fidelity leads to low visibility of quantum operations. Here, we demonstrate an alternative method to achieve spin-to-charge conversion of ST 0 qubit states using energy-selective tunneling between doubly occupied quantum dots (QDs) and electron reservoirs. We demonstrate a single-shot measurement fidelity of 90% and an S-T 0 oscillation visibility of 81% at a field gradient of 100 mT (~500 MHz h (g*•μ B) −1); this allows single-shot readout with full electron charge signal contrast and, at the same time, long and tunable measurement time with negligible effect of relaxation even at strong magnetic field gradients. Using an rf-sensor positioned opposite to the QD array, we apply this method to two ST 0 qubits and show high-visibility readout of two individual single-qubit gate operations is possible with a single rf single-electron transistor sensor. We expect our measurement scheme for two-electron spin states can be applied to various hosting materials and provides a simplified and complementary route for multiple qubit state detection with high accuracy in QD-based quantum computing platforms.

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“…Obtained this way initialization is not accurate and takes at least a couple of nanoseconds. However, to initialize a qubit to a known state for further operations, a high fidelity initialization procedure is necessary 20 . Additionally, to perform quantum er-ror correction certain ancillary qubits must be continuously reinitialized in ultra-short (relatively to decoherence) timescales 21 .…”

Section: Introductionmentioning

confidence: 99%

Ultrafast Spin Initialization in a Gated InSb Nanowire Quantum Dot

et al. 2019

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We propose a fast and accurate spin initialization method for a single electron trapped in an electrostatic quantum dot. The dot is created in a nanodevice composed of a catalytically grown indium antimonide (InSb) nanowire and nearby gates to which control voltages are applied. Initially we insert a single electron of arbitrary spin into the wire. Operations on spin are performed using the Rashba spin-orbit interaction induced by an electric field. First, a single pulse of voltages applied to lateral gates is used to split the electron wavepacket into two parts with opposite spin orientations. Next, another voltage pulse applied to the remaining gates rotates spins of both parts in opposite directions by π/2. This way, initially opposite spin parts eventually point in the same direction, along the axis of the quantum wire. We thus set spin in a predefined direction regardless of its initial orientation. This is achieved in time less than 60 ps without the use of microwaves, photons or external magnetic fields.

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A fast quantum interface between different spin qubit encodings

Cited by 31 publications

References 36 publications

Quantum non-demolition readout of an electron spin in silicon

Quantum non-demolition readout of an electron spin in silicon

Robust energy-selective tunneling readout of singlet-triplet qubits under large magnetic field gradient

Ultrafast Spin Initialization in a Gated InSb Nanowire Quantum Dot

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