@article{Bui2024,

title = {All-Electrical Driving and Probing of Dressed States in a Single Spin},

author = {Hong T Bui and Christoph Wolf and Yu Wang and Masahiro Haze and Arzhang Ardavan and Andreas J Heinrich and Soo Hyon Phark},

doi = {10.1021/acsnano.4c00196},

issn = {1936086X},

year  = {2024},

date = {2024-05-01},

urldate = {2024-05-01},

journal = {ACS Nano},

volume = {18},

number = {19},

pages = {12187–12193},

publisher = {American Chemical Society (ACS)},

abstract = {The subnanometer distance between tip and sample in a scanning tunneling microscope (STM) enables the application of very large electric fields with a strength as high as ∼1 GV/m. This has allowed for efficient electrical driving of Rabi oscillations of a single spin on a surface at a moderate radiofrequency (RF) voltage on the order of tens of millivolts. Here, we demonstrate the creation of dressed states of a single electron spin localized in the STM tunnel junction by using resonant RF driving voltages. The read-out of these dressed states was achieved all electrically by a weakly coupled probe spin. Our work highlights the strength of the atomic-scale geometry inherent to the STM that facilitates the creation and control of dressed states, which are promising for the design of atomic scale quantum devices using individual spins on surfaces.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wang2023a,

title = {An atomic-scale multi-qubit platform},

author = {Yu Wang and Yi Chen and Hong T Bui and Christoph Wolf and Masahiro Haze and Cristina Mier and Jinkyung Kim and Deung-Jang Choi and Christopher P Lutz and Yujeong Bae and Soo-Hyon Phark and Andreas J Heinrich},

url = {https://www.science.org/doi/10.1126/science.ade5050},

doi = {10.1126/science.ade5050},

issn = {0036-8075},

year  = {2023},

date = {2023-10-01},

urldate = {2023-10-01},

journal = {Science},

volume = {382},

number = {6666},

pages = {87–92},

abstract = {Individual electron spins in solids are promising candidates for quantum science and technology, where bottom-up assembly of a quantum device with atomically precise couplings has long been envisioned. Here, we realized atom-by-atom construction, coherent operations, and readout of coupled electron-spin qubits using a scanning tunneling microscope. To enable the coherent control of “remote” qubits that are outside of the tunnel junction, we complemented each electron spin with a local magnetic field gradient from a nearby single-atom magnet. Readout was achieved by using a sensor qubit in the tunnel junction and implementing pulsed double electron spin resonance. Fast single-, two-, and three-qubit operations were thereby demonstrated in an all-electrical fashion. Our angstrom-scale qubit platform may enable quantum functionalities using electron spin arrays built atom by atom on a surface.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Phark2023a,

title = {Electric-Field-Driven Spin Resonance by On-Surface Exchange Coupling to a Single-Atom Magnet},

author = {Soo Phark and Hong Thi Bui and Alejandro Ferrón and Joaquin Fernández-Rossier and Jose Reina-Gálvez and Christoph Wolf and Yu Wang and Kai Yang and Andreas J. Heinrich and Christopher P Lutz},

doi = {10.1002/advs.202302033},

issn = {21983844},

year  = {2023},

date = {2023-09-01},

urldate = {2023-09-01},

journal = {Advanced Science},

volume = {10},

number = {27},

pages = {e2302033},

abstract = {Coherent control of individual atomic and molecular spins on surfaces has recently been demonstrated by using electron spin resonance (ESR) in a scanning tunneling microscope (STM). Here, a combined experimental and modeling study of the ESR of a single hydrogenated Ti atom that is exchange-coupled to a Fe adatom positioned 0.6–0.8 nm away by means of atom manipulation is presented. Continuous wave and pulsed ESR of the Ti spin show a Rabi rate with two contributions, one from the tip and the other from the Fe, whose spin interactions with Ti are modulated by the radio-frequency electric field. The Fe contribution is comparable to the tip, as revealed by its dominance when the tip is retracted, and tunable using a vector magnetic field. The new ESR scheme allows on-surface individual spins to be addressed and coherently controlled without the need for magnetic interaction with a tip. This study establishes a feasible implementation of spin-based multi-qubit systems on surfaces.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Phark2023,

title = {Double-Resonance Spectroscopy of Coupled Electron Spins on a Surface},

author = {Soo Hyon Phark and Yi Chen and Hong T Bui and Yu Wang and Masahiro Haze and Jinkyung Kim and Yujeong Bae and Andreas J Heinrich and Christoph Wolf},

url = {https://pubs.acs.org/doi/10.1021/acsnano.3c04754},

doi = {10.1021/acsnano.3c04754},

issn = {1936086X},

year  = {2023},

date = {2023-07-01},

urldate = {2023-07-01},

journal = {ACS Nano},

volume = {17},

number = {14},

pages = {14144–14151},

abstract = {Scanning-tunneling microscopy (STM) combined with electron spin resonance (ESR) has enabled single-spin spectroscopy with nanoelectronvolt energy resolution and angstrom-scale spatial resolution, which allows quantum sensing and magnetic resonance imaging at the atomic scale. Extending this spectroscopic tool to a study of multiple spins, however, is nontrivial due to the extreme locality of the STM tunnel junction. Here we demonstrate double electron-electron spin resonance spectroscopy in an STM for two coupled atomic spins by simultaneously and independently driving them using two continuous-wave radio frequency voltages. We show the ability to drive and detect the resonance of a spin that is remote from the tunnel junction while read-out is achieved via the spin in the tunnel junction. Open quantum system simulations for two coupled spins reproduce all double-resonance spectra and further reveal a relaxation time of the remote spin that is longer by an order of magnitude than that of the local spin in the tunnel junction. Our technique can be applied to quantum-coherent multi-spin sensing, simulation, and manipulation in engineered spin structures on surfaces.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Wang2023,

title = {Universal quantum control of an atomic spin qubit on a surface},

author = {Yu Wang and Masahiro Haze and Hong T Bui and We-Hyo Soe and Herve Aubin and Arzhang Ardavan and Andreas J Heinrich and Soo-Hyon Phark},

url = {https://www.nature.com/articles/s41534-023-00716-6},

doi = {10.1038/s41534-023-00716-6},

issn = {2056-6387},

year  = {2023},

date = {2023-05-01},

urldate = {2023-05-01},

journal = {npj Quantum Information},

volume = {9},

number = {1},

pages = {48},

publisher = {Springer Science and Business Media LLC},

abstract = {Scanning tunneling microscopy (STM) enables the bottom-up fabrication of tailored spin systems on a surface that are engineered with atomic precision. When combining STM with electron spin resonance (ESR), these single atomic and molecular spins can be controlled quantum-coherently and utilized as electron-spin qubits. Here we demonstrate universal quantum control of such a spin qubit on a surface by employing coherent control along two distinct directions, achieved with two consecutive radio-frequency (RF) pulses with a well-defined phase difference. We first show transformations of each Cartesian component of a Bloch vector on the quantization axis, followed by ESR-STM detection. Then we demonstrate the ability to generate an arbitrary superposition state of a single spin qubit by using two-axis control schemes, in which experimental data show excellent agreement with simulations. Finally, we present an implementation of two-axis control in dynamical decoupling. Our work extends the scope of STM-based pulsed ESR, highlighting the potential of this technique for quantum gate operations of electron-spin qubits on a surface.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}