Neutron transmutation doping of isotopically engineered Ge

Donor electron spins in semiconductors make exceptional quantum bits because of their long coherence times and compatibility with industrial fabrication techniques. Despite many advances in donor-based qubit technology, it remains difficult to selectively manipulate single donor electron spins. Here, we show that by replacing the prevailing semiconductor host material (silicon) with germanium, donor electron spin qubits can be electrically tuned by more than an ensemble linewidth, making them compatible with gate addressable quantum computing architectures. Using X-band pulsed electron spin resonance, we measured the Stark effect for donor electron spins in germanium. We resolved both spin-orbit and hyperfine Stark shifts and found that at 0.4 T, the spin-orbit Stark shift dominates. The spin-orbit Stark shift is highly anisotropic, depending on the electric field orientation relative to the crystal axes and external magnetic field. When the Stark shift is maximized, the spin-orbit Stark parameter is four orders of magnitude larger than in silicon. At select orientations a hyperfine Stark effect was also resolved and is an order of magnitude larger than in silicon. We report the Stark parameters for 75 As and 31 P donor electrons and compare them to the available theory. Our data reveal that 31 P donors in germanium can be tuned by at least four times the ensemble linewidth making germanium an appealing new host material for spin qubits that offers major advantages over silicon.

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“…73 Ge [9,32,33]. This crystal was neutron transmutation doped to a density of 3 × 10 15 75 As donors/cm 3 .…”

Section: Experimental Methodsmentioning

confidence: 99%

Large Stark tuning of donor electron spin qubits in germanium

et al. 2016

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“…17. Briefly, high-purity single crystals consisting of controlled mixtures of 70 Ge and 74 Ge were first grown using our modified vertical Bridgman method.…”

Section: Methodsmentioning

confidence: 99%

“…17 This method enables us to control independently the majority N MJ and minority N MN impurity concentrations, i.e., the net-impurity concentration N MJ ϪN MN and the compensation ratio KϭN MN /N MJ . Using this method, a series of p-type Ge ͑Ga,As͒ samples of constant N Net ϭ͓Ga͔Ϫ͓As͔ϭ5ϫ10 14 cm Ϫ3 , with K ranging between 0.082 and 0.87, was produced in order to study the electric-field broadening of the excitation lines of Ga acceptors at low temperatures.…”

Section: Introductionmentioning

confidence: 99%

Evidence for correlated hole distribution in neutron-transmutation-doped isotopically controlled germanium

et al. 1996

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We report on low-temperature infrared-absorption spectroscopy studies of compensated p-type Ge͑Ga,As͒ samples with varying doping compensation ratios. Previous difficulties in preparing appropriate samples are overcome by neutron-transmutation doping of high-purity, isotopically controlled germanium composed exclusively of 70 Ge and 74 Ge, viz. 70 Ge x 74 Ge 1Ϫx . With this technique, we have produced a series of crystals with compensation ratios between 0.082 and 0.87, while maintaining the net-acceptor concentration ͓Ga͔-͓As͔ constant at 5ϫ10 14 cm Ϫ3 . The observed excitation lines of Ga acceptors broaden linearly with the ionized impurity concentration due to the quadrupole interactions between Ga bound holes and the electric-field gradient. Experimental linewidths are quantitatively compared with existing theories of electric-field broadening developed in the context of donor transitions. We find excellent agreement with the theory based on the correlated distribution of ionized impurity centers.

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“…The total detector mass is 741 kg, corresponding to 206 kg of the 130 Te isotope. 3×3×1 mm 3 NTD Ge thermistors [16] have been glued on each module as temperature sensors. Each bolometer is also instrumented with a Joule heater, which is used to inject in each bolometer a known amount of energy at regular time intervals for offline thermal gain instability correction [17].…”

Section: Cuorementioning

confidence: 99%

CUORE-0 results and prospects for the CUORE experiment

Cremonesi

Artusa²,

Avignone³

et al. 2015

AIP Conference Proceedings

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Abstract.With 741 kg of TeO 2 crystals and an excellent energy resolution of 5 keV (0.2%) at the region of interest, the CUORE (Cryogenic Underground Observatory for Rare Events) experiment aims at searching for neutrinoless double beta decay of 130 Te with unprecedented sensitivity. Expected to start data taking in 2015, CUORE is currently in an advanced construction phase at LNGS. CUORE projected neutrinoless double beta decay half-life sensitivity is 1.6 × 10 26 y at 1σ (9.5 × 10 25 y at the 90 % confidence level), in five years of live time, corresponding to an upper limit on the effective Majorana mass in the range 40-100 meV (50-130 meV). Further background rejection with auxiliary bolometric detectors could improve CUORE sensitivity and competitiveness of bolometric detectors towards a full analysis of the inverted neutrino mass hierarchy. CUORE-0 was built to test and demonstrate the performance of the upcoming CUORE experiment. It consists of a single CUORE tower (52 TeO 2 bolometers of 750 g each, arranged in a 13 floor structure) constructed strictly following CUORE recipes both for materials and assembly procedures. An experiment its own, CUORE-0 is expected to reach a sensitivity to the β β (0ν) half-life of 130 Te around 3×10 24 y in one year of live time. We present an update of the data, corresponding to an exposure of 18.1 kg y. An analysis of the background indicates that the CUORE performance goal is satisfied while the sensitivity goal is within reach.

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Neutron transmutation doping of isotopically engineered Ge

Cited by 32 publications

References 12 publications

Large Stark tuning of donor electron spin qubits in germanium

Large Stark tuning of donor electron spin qubits in germanium

Evidence for correlated hole distribution in neutron-transmutation-doped isotopically controlled germanium

CUORE-0 results and prospects for the CUORE experiment

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