Microstrip superconducting quantum interference device radio-frequency amplifier: Effects of negative feedback on input impedance

Hover, David; Sendelbach, S.; McDermott, Robert

doi:10.1063/1.3114419

Cited by 6 publications

(7 citation statements)

References 13 publications

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“…There are other implementations of directional amplifiers but they have so far met difficulties in satisfying all the aforementioned criteria. For example, SQUID-based directional amplifiers, such as the microstrip SQUID amplifier (MSA) [18][19][20] and the superconducting low-inductance undulatory galvanometer (SLUG) [21,22], dissipate energy on chip and have outof-band back-action which still requires using circulators in quantum measurements [23]. There is also a different type of directional amplifier known as the traveling-wave parametric amplifier in which the nonlinearity of kinetic inductance of superconducting transmission lines [24] or Josephson junctions [25] is exploited in order to parametrically amplify weak propagating signals.…”

Section: Plifiermentioning

confidence: 99%

Josephson Directional Amplifier for Quantum Measurement of Superconducting Circuits

et al. 2014

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We have realized a microwave quantum-limited amplifier that is directional and can therefore function without the front circulator needed in many quantum measurements. The amplification takes place in only one direction between the input and output ports. Directionality is achieved by multi-pump parametric amplification combined with wave interference. We have verified the device noise performances by using it to readout a superconducting qubit and observed quantum jumps. With an improved version of this device, qubit and preamplifer could be integrated on the same chip.PACS numbers: 84.30. Le, 85.25.Cp, 42.25.Hz Quantum non-demolition (QND) measurements often require probing a quantum system with a signal containing only a few photons [1]. Measuring such a weak signal with high fidelity in the microwave domain involves a high-gain, low-noise chain of amplifiers. However, stateof-the-art amplifiers, such as those based on high electron mobility transistors (HEMT), are not quantum-limited [2]; they add the noise equivalent of about 20 photons at the signal frequency when referred back to the input. They can also have strong in-band and out-of-band back-action on the quantum system. In an attempt to minimize the noise added by the output chain, quantumlimited amplifiers such as the Josephson bifurcation amplifier (JBA) [3, 4], Josephson parametric amplifier (JPA) [5, 6], and Josephson parametric converter (JPC) [7][8][9] have been recently developed and used as preamplifiers before the HEMT [10][11][12][13]. Unfortunately, these quantum-limited devices amplify in reflection [4,8,14] and some of them have in addition strong reflected tones, e.g. reflected pump tone in the JBA case, which cause undesirable back-action on the quantum system. These devices also do not protect the measured system from back-action originating higher up in the amplification chain. Thus, non-reciprocal devices such as circulators and isolators are required in these measurements both to separate input from output, and also to protect the quantum system from unwanted back-action.An illustration of the difference between reciprocal and non-reciprocal (NR) phenomena is shown in the cartoon in Fig. 1. Panel (a) illustrates the reciprocity symmetry in wave physics, which is known in daily-life as "you see the eyes which see you". In other words, a medium is reciprocal if its transmission coefficient for electromagnetic waves is invariant upon exchanging the source and the detector. Panel (b) on the other hand illustrates the less common phenomenon of non-reciprocity in which a certain medium or device breaks the reciprocity symmetry * Current address: IBM T. J. Watson Research Center, Yorktown Heights, New York 10598, USA.† Electronic address: michel.devoret@yale.edu allowing only the detector to see the source and not the opposite. To achieve non-reciprocity, circulators and isolators exploit a magneto-optical effect known as Faraday rotation, which relies on ferrites and permanent magnets, in order to distinguish between polarized waves pr...

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Section: Plifiermentioning

confidence: 99%

Josephson Directional Amplifier for Quantum Measurement of Superconducting Circuits

et al. 2014

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“…One example of a superconducting nonreciprocal element is the microstrip SQUID amplifier (MSA) [14][15][16][17][18][19][20]. The MSA is biased with a dc current and converts an ac flux signal at the input into an amplified voltage at the output.…”

Section: Introductionmentioning

confidence: 99%

Directional Amplification with a Josephson Circuit

et al. 2013

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Nonreciprocal devices perform crucial functions in many low-noise quantum measurements, usually by exploiting magnetic effects. In the proof-of-principle device presented here, on the other hand, two on-chip coupled Josephson parametric converters (JPCs) achieve directionality by exploiting the nonreciprocal phase response of the JPC in the transmission-gain mode. The nonreciprocity of the device is controlled in situ by varying the amplitude and phase difference of two independent microwave pump tones feeding the system. At the desired working point and for a signal frequency of 8.453 GHz, the device achieves a forward power gain of 15 dB within a dynamical bandwidth of 9 MHz, a reverse gain of À6 dB, and suppression of the reflected signal by 8 dB. We also find that the amplifier adds a noise equivalent to less than 1.5 photons at the signal frequency (referred back to the input). It can process up to 3 photons at the signal frequency per inverse dynamical bandwidth. With a directional amplifier operating along the principles of this device, qubit and readout preamplifier could be integrated on the same chip.

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“…While it is difficult to avoid some kind of negative or positive feedback by the finite inductance of the bond wires used to connect the SQUID washer to ground, 11 we believe that at lower frequencies (300 MHz), this contribution to possible feedback can be made negligible. To this end, we were using seven very short ($1 mm) bond wires in parallel to connect the SQUID washer to ground.…”

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confidence: 99%

“…Their estimated stray inductance of $150 pH introduces an impedance of 0.3 X (at 300 MHz), which is negligible to the $50 X output impedance. We measured the noise temperature of a few MSAs first without, and then with external negative feedback 11 (gain reduced by 4 dB) but did not observe a noticeable difference in their noise temperature.…”

mentioning

confidence: 99%

“…We measured the gain of our amplifiers with a scalar network analyzer; it was also used to determine the input impedance of our devices. 11,12 For frequencies below 1.5 GHz, a HP8970A noise figure meter was used to determine the noise temperature of our amplifiers, in combination with a calibrated HP346B noise source. For higher frequencies, we used the network analyzer as a receiver for the noise produced by the MSAs.…”

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Microstrip direct current superconducting quantum interference device radio frequency amplifier: Noise data

Schmidt

2012

Applied Physics Letters

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A series of about twenty superconducting quantum interference devices (SQUIDs) has been operated as microstrip-SQUID amplifiers (MSAs) at frequencies ranging from 100 MHz to 2 GHz to study the dependence of their gain and noise temperature on bias current and flux. The measured values were in good agreement with theory. The observed dependence of MSA gain and noise temperature on bias current and flux resembled the static transfer function of the SQUIDs. The gains are relatively insensitive to changes in bias current and bias flux; the noise temperature is strongly dependent on the bias flux.

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Microstrip superconducting quantum interference device radio-frequency amplifier: Effects of negative feedback on input impedance

Cited by 6 publications

References 13 publications

Josephson Directional Amplifier for Quantum Measurement of Superconducting Circuits

Josephson Directional Amplifier for Quantum Measurement of Superconducting Circuits

Directional Amplification with a Josephson Circuit

Microstrip direct current superconducting quantum interference device radio frequency amplifier: Noise data

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