56,565 research outputs found
Are Patent Laws Harmful to Developing Countries? Evidence from China
Has upgrading and enforcing its patent laws slowed China’s economic growth? The answer we draw from detailed analysis of provincial aggregate data covering roughly the period 1990 through 2007 is strongly negative, but understanding the channels through which stricter protection of intellectual property rights has contributed to more rapid productivity growth is elusive. Our best estimate of the direct impact of the 1992 and 2001 patent laws on TFP growth amounts to not quite 15 percent of the average TFP growth rate over the period, but a much larger share of TFP growth is associated with enactment of the laws in a simple interpretation of our empirical investigation. We estimate that virtually none of the laws’ impact on TFP growth can be directly associated with increased quantity of FDI or R&D, although both series are strongly positively correlated with promulgation of the patent laws. We infer that amount of technology transfer through a FDI and the focus of R&D activity, decline of state ownership and increased marketization, growth of the human capital stock, and movement of the labor force from agriculture to manufacturing and service industries are all processes that were encouraged and whose effect has been magnified by stronger IPR protection. Moreover, adopting and enforcing the patent laws probably cannot be treated as an independent event with causation running in only one direction to China’s economic development..Patent law, Intellectual Property Rights, TRIPS, TFP Growth
Impurity scattering in a d-wave superconductor
The influence of (non-magnetic and magnetic) impurities on the transition
temperature of a d-wave superconductor is studied anew within the framework of
BCS theory. Pairing interaction decreases linearly with the impurity
concentration. Accordingly suppression is proportional to the
(potential or exchange) scattering rate, , due to impurities. The
initial slope versus is found to depend on the superconductor contrary
to Abrikosov-Gor'kov type theory. Near the critical impurity concentration
drops abruptly to zero. Because the potential scattering rate is
generally much larger than the exchange scattering rate, magnetic impurities
will also act as non-magnetic impurities as far as the decrease is
concerned. The implication for the impurity doping effect in high
superconductors is also discussed.Comment: 12 pages and 1 figure, PlainTex, submitted to Mod. Phys. Lett. B, For
more information, please see "http://taesan.kaist.ac.kr/~yjkim
Probing Coherent Vibrations of Organic Phosphonate Radical Cations with Femtosecond Time-Resolved Mass Spectrometry
Organic phosphates and phosphonates are present in a number of cellular components that can be damaged by exposure to ionizing radiation. This work reports femtosecond time-resolved mass spectrometry (FTRMS) studies of three organic phosphonate radical cations that model the DNA sugar-phosphate backbone: dimethyl methylphosphonate (DMMP), diethyl methylphosphonate (DEMP), and diisopropyl methylphosphonate (DIMP). Upon ionization, each molecular radical cation exhibits unique oscillatory dynamics in its ion yields resulting from coherent vibrational excitation. DMMP has particularly well-resolved 45 fs (732 ± 28 cm−1) oscillations with a weak feature at 610–650 cm−1, while DIMP exhibits bimodal oscillations with a period of ∼55 fs and two frequency features at 554 ± 28 and 670–720 cm−1. In contrast, the oscillations in DEMP decay too rapidly for effective resolution. The low- and high-frequency oscillations in DMMP and DIMP are assigned to coherent excitation of the symmetric O–P–O bend and P–C stretch, respectively. The observation of the same ionization-induced coherently excited vibrations in related molecules suggests a possible common excitation pathway in ionized organophosphorus compounds of biological relevance, while the distinct oscillatory dynamics in each molecule points to the potential use of FTRMS to distinguish among fragment ions produced by related molecules
Probing Coherent Vibrations of Organic Phosphonate Radical Cations with Femtosecond Time-Resolved Mass Spectrometry
Organic phosphates and phosphonates are present in a number of cellular components that can be damaged by exposure to ionizing radiation. This work reports femtosecond time-resolved mass spectrometry (FTRMS) studies of three organic phosphonate radical cations that model the DNA sugar-phosphate backbone: dimethyl methylphosphonate (DMMP), diethyl methylphosphonate (DEMP), and diisopropyl methylphosphonate (DIMP). Upon ionization, each molecular radical cation exhibits unique oscillatory dynamics in its ion yields resulting from coherent vibrational excitation. DMMP has particularly well-resolved 45 fs (732 ± 28 cm−1) oscillations with a weak feature at 610–650 cm−1, while DIMP exhibits bimodal oscillations with a period of ∼55 fs and two frequency features at 554 ± 28 and 670–720 cm−1. In contrast, the oscillations in DEMP decay too rapidly for effective resolution. The low- and high-frequency oscillations in DMMP and DIMP are assigned to coherent excitation of the symmetric O–P–O bend and P–C stretch, respectively. The observation of the same ionization-induced coherently excited vibrations in related molecules suggests a possible common excitation pathway in ionized organophosphorus compounds of biological relevance, while the distinct oscillatory dynamics in each molecule points to the potential use of FTRMS to distinguish among fragment ions produced by related molecules
A Reconfigurable Gate Architecture for Si/SiGe Quantum Dots
We demonstrate a reconfigurable quantum dot gate architecture that
incorporates two interchangeable transport channels. One channel is used to
form quantum dots and the other is used for charge sensing. The quantum dot
transport channel can support either a single or a double quantum dot. We
demonstrate few-electron occupation in a single quantum dot and extract
charging energies as large as 6.6 meV. Magnetospectroscopy is used to measure
valley splittings in the range of 35-70 microeV. By energizing two additional
gates we form a few-electron double quantum dot and demonstrate tunable tunnel
coupling at the (1,0) to (0,1) interdot charge transition.Comment: Related papers at http://pettagroup.princeton.ed
Scalable gate architecture for densely packed semiconductor spin qubits
We demonstrate a 12 quantum dot device fabricated on an undoped Si/SiGe
heterostructure as a proof-of-concept for a scalable, linear gate architecture
for semiconductor quantum dots. The device consists of 9 quantum dots in a
linear array and 3 single quantum dot charge sensors. We show reproducible
single quantum dot charging and orbital energies, with standard deviations less
than 20% relative to the mean across the 9 dot array. The single quantum dot
charge sensors have a charge sensitivity of 8.2 x 10^{-4} e/root(Hz) and allow
the investigation of real-time charge dynamics. As a demonstration of the
versatility of this device, we use single-shot readout to measure a spin
relaxation time T1 = 170 ms at a magnetic field B = 1 T. By reconfiguring the
device, we form two capacitively coupled double quantum dots and extract a
mutual charging energy of 200 microeV, which indicates that 50 GHz two-qubit
gate operation speeds are feasible
X-shaped and Y-shaped Andreev resonance profiles in a superconducting quantum dot
The quasi-bound states of a superconducting quantum dot that is weakly
coupled to a normal metal appear as resonances in the Andreev reflection
probability, measured via the differential conductance. We study the evolution
of these Andreev resonances when an external parameter (such as magnetic field
or gate voltage) is varied, using a random-matrix model for the
scattering matrix. We contrast the two ensembles with broken time-reversal
symmetry, in the presence or absence of spin-rotation symmetry (class C or D).
The poles of the scattering matrix in the complex plane, encoding the center
and width of the resonance, are repelled from the imaginary axis in class C. In
class D, in contrast, a number of the poles has zero real
part. The corresponding Andreev resonances are pinned to the middle of the gap
and produce a zero-bias conductance peak that does not split over a range of
parameter values (Y-shaped profile), unlike the usual conductance peaks that
merge and then immediately split (X-shaped profile).Comment: Contribution for the JETP special issue in honor of A.F. Andreev's
75th birthday. 9 pages, 8 figure
A Coherent Spin-Photon Interface in Silicon
Electron spins in silicon quantum dots are attractive systems for quantum
computing due to their long coherence times and the promise of rapid scaling
using semiconductor fabrication techniques. While nearest neighbor exchange
coupling of two spins has been demonstrated, the interaction of spins via
microwave frequency photons could enable long distance spin-spin coupling and
"all-to-all" qubit connectivity. Here we demonstrate strong-coupling between a
single spin in silicon and a microwave frequency photon with spin-photon
coupling rates g_s/(2\pi) > 10 MHz. The mechanism enabling coherent spin-photon
interactions is based on spin-charge hybridization in the presence of a
magnetic field gradient. In addition to spin-photon coupling, we demonstrate
coherent control of a single spin in the device and quantum non-demolition spin
state readout using cavity photons. These results open a direct path toward
entangling single spins using microwave frequency photons
Input-output theory for spin-photon coupling in Si double quantum dots
The interaction of qubits via microwave frequency photons enables
long-distance qubit-qubit coupling and facilitates the realization of a
large-scale quantum processor. However, qubits based on electron spins in
semiconductor quantum dots have proven challenging to couple to microwave
photons. In this theoretical work we show that a sizable coupling for a single
electron spin is possible via spin-charge hybridization using a magnetic field
gradient in a silicon double quantum dot. Based on parameters already shown in
recent experiments, we predict optimal working points to achieve a coherent
spin-photon coupling, an essential ingredient for the generation of long-range
entanglement. Furthermore, we employ input-output theory to identify observable
signatures of spin-photon coupling in the cavity output field, which may
provide guidance to the experimental search for strong coupling in such
spin-photon systems and opens the way to cavity-based readout of the spin
qubit
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