Ultrafast Manipulation of Electron Spin Coherence

Gupta, J. A.; Knobel, R.; Samarth, N.; Awschalom, D. D.

doi:10.1126/science.1061169

Cited by 267 publications

(213 citation statements)

References 18 publications

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“…Indeed the field of spin-dependent transport, or spintronics, is the fastest growing area of quantum electronics due largely to the possible applications to conventional information processing and storage 31 . The possible application to quantum computing of course has been noticed by many 32 .…”

Section: Spintronicsmentioning

confidence: 99%

Quantum technology: the second quantum revolution

Dowling

Milburn

2003

Philosophical Transactions of the Royal Society of London. Seri

820

609

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Abstract.We are currently in the midst of a second quantum revolution. The first quantum revolution gave us new rules that govern physical reality. The second quantum revolution will take these rules and use them to develop new technologies. In this review we discuss the principles upon which quantum technology is based and the tools required to develop it. We discuss a number of examples of research programs that could deliver quantum technologies in coming decades including; quantum information technology, quantum electromechanical systems, coherent quantum electronics, quantum optics and coherent matter technology.

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Section: Spintronicsmentioning

confidence: 99%

Quantum technology: the second quantum revolution

Dowling

Milburn

2003

Philosophical Transactions of the Royal Society of London. Seri

820

609

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“…The optical Stark effect has been applied to manipulate the spin/pseudospin in quantum systems, such as atomic quantum gases 19 , quantum dots 20,21 , and III-V quantum wells 22 . Here we utilize this strong pseudomagnetic field in monolayer WSe 2 to rotate the valley pseudospin in the superposition plane of K and K valley polarizations (Fig.…”

mentioning

confidence: 99%

Optical manipulation of valley pseudospin

Ye¹,

Sun²,

Heinz³

2016

Nature Phys

233

223

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The coherent manipulation of spin and pseudospin underlies existing and emerging quantum technologies, including quantum communication and quantum computation 1,2 . Valley polarization, associated with the occupancy of degenerate, but quantum mechanically distinct valleys in momentum space, closely resembles spin polarization and has been proposed as a pseudospin carrier for the future quantum electronics 3,4 . Valley exciton polarization has been created in the transition metal dichalcogenide monolayers using excitation by circularly polarized light and has been detected both optically 5-7 and electrically 8 . In addition, the existence of coherence in the valley pseudospin has been identified experimentally 9 . The manipulation of such valley coherence has, however, remained out of reach. Here we demonstrate all-optical control of the valley coherence by means of the pseudomagnetic field associated with the optical Stark e ect. Using below-bandgap circularly polarized light, we rotate the valley exciton pseudospin in monolayer WSe 2 on the femtosecond timescale. Both the direction and speed of the rotation can be manipulated optically by tuning the dynamic phase of excitons in opposite valleys. This study unveils the possibility of generation, manipulation, and detection of the valley pseudospin by coupling to photons.The broken inversion symmetry in monolayer transition metal dichalcogenide (TMDC) crystals in the semiconducting MX 2 (M = Mo, W; X = S, Se) family gives rise to a nontrivial Berry phase at the K and K valleys in momentum space 10 , where the optically accessible direct bandgap occurs in these materials 11,12 . This Berry phase, together with the angular momentum of the atomic orbitals, leads to different optical selection rules for the two valleys: excitons in the K valley couple to left-circularly polarized photons, while excitons in the K valley couple to right-circularly polarized photons, thus permitting the optical generation of valley polarization through control of the helicity of light [5][6][7] . Moreover, when a TMDC monolayer is excited with linearly polarized light, a coherent superposition state is established between the K and K valley excitons 9 . Such a coherent state can, in principle, be manipulated by lifting the energy degeneracy between valleys through the breaking of time-reversal symmetry in the material. In this regard, d.c. magnetic fields have been applied to achieve a valley splitting of a few meV [13][14][15][16] . Circularly polarized light also breaks time-reversal symmetry, and researchers have used it to create larger valley splittings, corresponding to pseudomagnetic fields up to 60 T (refs 17,18). In addition, this optical approach permits us to access the ultrafast timescale: in this work, we demonstrate the coherent manipulation of the valley pseudospin on the femtosecond timescale.The optical Stark effect has been applied to manipulate the spin/pseudospin in quantum systems, such as atomic quantum gases 19 , quantum dots 20,21 , and III-V quantum wells 22 . H...

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“…1 results from individual laser pulses. This term corresponds to spin rotations induced by a DC magnetic field along the x-axis, as extensively investigated in earlier studies [7][8][9][10][11][12][13][14] . The second term in Eq.…”

Section: Physical Mechanisms Of Optical Spin Rotationmentioning

confidence: 99%

“…The coherent optical interactions can also be exploited for the generation of spin-photon quantum entanglement in atomic as well as solid-state spin systems [3][4][5][6] . Optical spin control using ultrafast laser pulses has been demonstrated in various semiconductor systems [7][8][9][10][11][12][13] and also in trapped ions 14 . In these experiments, individual off-resonant laser pulses act like an effective DC magnetic field along the optical axis, inducing a spin rotation about the fixed axis.…”

Section: Introductionmentioning

confidence: 99%

Quantum control of electron spins in the two-dimensional electron gas of a CdTe quantum well with a pair of Raman-resonant phase-locked laser pulses

2011

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We demonstrated optical spin control of a two-dimensional electron gas in a modulationdoped CdTe quantum well by driving a spin-flip Raman transition with a pair of phase-locked laser pulses. In contrast to single-pulse optical spin control, which features a fixed spin-rotation axis, manipulation of the initial relative phase of the pulse pair enables us to control the axis of the optical spin rotation. We show that the Raman pulse pair acts like an effective microwave field, mapping the relative optical phase onto the phase of the electron spin polarization and making possible ultrafast, all-optical, and full quantum control of the electron spins.2

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Ultrafast Manipulation of Electron Spin Coherence

Cited by 267 publications

References 18 publications

Quantum technology: the second quantum revolution

Quantum technology: the second quantum revolution

Optical manipulation of valley pseudospin

Quantum control of electron spins in the two-dimensional electron gas of a CdTe quantum well with a pair of Raman-resonant phase-locked laser pulses

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