 , J. Fabian , and S. Das Sarma , Rev. Mod. Phys. 00 , 000 ( 0000 ). RMPHAT 0000-0000 00.0000/RevModPhys.00.000 [00] 00 R. Jansen , Nat. Mater. 00 , 000 ( 0000 ). NMAACR 0000-0000 00.0000/nmat0000 [00] 00 See Supplemental Material at http://link.aps.org/supplemental/00.0000/PhysRevLett.000.000000 for details on sample growth, experimental techniques, additional data and analysis. [00] 00 D. Weiss , K. von Klitzing , K. Ploog , and G. Weimann , Europhys. Lett. 0 , 000 ( 0000 ). EULEEJ 0000-0000 00.0000/0000-0000/0/0/000 [00] 00 R. R. Gerhardts , D. Weiss , and K. von Klitzing , Phys. Rev. Lett. 00 , 0000 ( 0000 ). PRLTAO 0000-0000 00.0000/PhysRevLett.00.0000 [00] 00 R. W. Winkler , J. P. Kotthaus , and K. Ploog , Phys. Rev. Lett. 00 , 0000 ( 0000 ). PRLTAO 0000-0000 00.0000/PhysRevLett.00.0000 [00] 00 C. W. J. Beenakker , Phys. Rev. Lett. 00 , 0000 ( 0000 ). PRLTAO 0000-0000 00.0000/PhysRevLett.00.0000 [00] 00 J. H. Davies and I. A. Larkin , Phys. Rev. B 00 , 0000 ( 0000 ). PRBMDO 0000-0000 00.0000/PhysRevB.00.0000 [00] 00 E. Skuras , A. R. Long , I. A. Larkin , J. H. Davies , and M. C. Holland , Appl. Phys. Lett. 00 , 000 ( 0000 ). APPLAB 0000-0000 00.0000/0.000000 [00] 00 A. R. Long , E. Skuras , S. Vallis , R. Cusco , I. A. Larkin , J. H. Davies , and M. C. Holland , Phys. Rev. B 00 , 0000 ( 0000 ). PRBMDO 0000-0000 00.0000/PhysRevB.00.0000 [00] 00 J. F. Nye , The Physical Properties of Crystals ( Oxford University Press , New York, 0000 ). [00] 00 O. Gunawan , Y. P. Shkolnikov , E. P. De Poortere , E. Tutuc , and M. Shayegan , Phys. Rev. Lett. 00 , 000000 ( 0000 ). PRLTAO 0000-0000 00.0000/PhysRevLett.00.000000 [00] 00 T. Gokmen , M. Padmanabhan , and M. Shayegan , Nat. Phys. 0 , 000 ( 0000 ). NPAHAX 0000-0000 00.0000/nphys0000 [00] 00 T. Gokmen , M. Padmanabhan , O. Gunawan , Y. P. Shkolnikov , K. Vakili , E. P. De Poortere , and M. Shayegan , Phys. Rev. B 00 , 000000 ( 0000 ). PRBMDO 0000-0000 00.0000/PhysRevB.00.000000 [00] 00 See Sec. IV in Supplemental Material at for http://link.aps.org/supplemental/00.0000/PhysRevLett.000.000000 , the method used to estimate the valley modulation amplitude. This section includes Refs. [00,00]. [00] 00 P. H. Beton , E. S. Alves , P. C. Main , L. Eaves , M. W. Dellow , M. Henini , O. H. Hughes , S. P. Beaumont , and C. D. W. Wilkinson , Phys. Rev. B 00 , 0000 ( 0000 ). PRBMDO 0000-0000 00.0000/PhysRevB.00.0000 [00] 00 A. Endo and Y. Iye , Phys. Rev. B 00 , 000000 ( 0000 ). PRBMDO 0000-0000 00.0000/PhysRevB.00.000000 [00] Our estimate is based on the following considerations. As seen in Figs. 0(b) and 0(c) , a strain of | ϵ | ≃ 0.0 × 00 - 0 can completely valley polarize the 0DES, i.e., to transfer 000% density to one valley for n ≃ 0.0 × 00 00 cm - 0 . (Even less strain would be needed for smaller 0DES densities.) It then follows from a valley modulation of ≃ 00 % that the modulated local strain responsible for the COs is ≃ 0.00 × 00 - 0 . Now, a strip of Ti on a GaAs substrate is expected to produce 00 - 0 of local surface strain [00,00] which, in principle, should completely valley polarize each AlAs 0DES strip illustrated in Figs. 0(c) and 0(d) . [00] 00 K. von Klitzing , Rev. Mod. Phys. 00 , 000 ( 0000 ). RMPHAT 0000-0000 00.0000/RevModPhys.00.000 [00] 00 R. M. Lutchyn , J. D. Sau , and S. Das Sarma , Phys. Rev. Lett. 000 , 000000 ( 0000 ). PRLTAO 0000-0000 00.0000/PhysRevLett.000.000000 [00] 00 Y. Oreg , G. Refael , and F. von Oppen , Phys. Rev. Lett. 000 , 000000 ( 0000 ). PRLTAO 0000-0000 00.0000/PhysRevLett.000.000000 [00] 00 S. Das Sarma , M. Freedman , and C. Nayak , npj Quantum Inf. 0 , 00000 ( 0000 ). 0000-0000 00.0000/npjqi.0000.0 [00] 00 T. Karzig , C. Knapp , R. M. Lutchyn , P. Bonderson , M. B. Hastings , C. Nayak , J. Alicea , K. Flensberg , S. Plugge , Y. Oreg , C. M. Marcus , and M. H. Freedman , Phys. Rev. B 00 , 000000 ( 0000 ). PRBMDO 0000-0000 00.0000/PhysRevB.00.000000 [00] 00 A. F. Young , J. D. Sanchez-Yamagishi , B. M. Hunt , S. H. Choi , K. Watanabe , T. Taniguchi , R. C. Ashoori , and P. Jarillo-Herrero , Nature (London) 000 , 000 ( 0000 ). NATUAS 0000-0000 00.0000/nature00000 [00] 00 J. D. Sanchez-Yamagishi , J. Y. Luo , A. F. Young , B. M. Hunt , K. Watanabe , T. Taniguchi , R. C. Ashoori , and P. Jarillo-Herrero , Nat. Nanotechnol. 00 , 000 ( 0000 ). NNAABX 0000-0000 00.0000/nnano.0000.000 [00] 00 Y. Ronen , Y. Cohen , D. Banitt , M. Heiblum , and V. Umansky , Nat. Phys. 00 , 000 ( 0000 ). NPAHAX 0000-0000 00.0000/s00000-000-0000-0 Funding Information: We acknowledge support through the National Science Foundation (Grants No.ECCS 0000000 and No.DMR 0000000) for measurements. For sample fabrication and characterization, we alsoacknowledge the National Science Foundation (Grant No.MRSEC DMR 0000000), the Gordon and Betty Moore Foundation (Grant No.GBMF0000), and the Department of Energy Basic Energy Sciences (DEFG00-00-ER00000). Publisher Copyright: {\textcopyright} 0000 American 