Massachusetts Institute of Technology

Jagadeesh S Moodera

Lisa Kinder

Patrick A Lee

Robert H Meservey

Yota Takamura

Janusz Nowak

Juan Pedro Cascales Sandoval

Terrilyn Wong

Peng Wei

Karthik Venkataraman

Patrick LeClair

Sujit Manna

Heejae Shim

Under certain conditions, a fermion in a superconductor can separate in space into two parts known as Majorana zero modes, which are immune to decoherence from local noise sources and are attractive building blocks for quantum computers. Here we disclose a metal-based heterostructure platform to produce these Majorana zero modes which utilizes the surface states of certain metals in combination with a ferromagnetic insulator and a superconductor. This platform has the advantage of having a robust energy scale and the possibility of realizing complex circuit designs using lithographic methods. The Majorana zero modes are interrogated using planar tunnel junctions and electrostatic gates to selectively tunnel into designated pairs of Majorana zero modes. We give example of qubit designs and circuits that are particularly suitable for the metal-based heterostructures.

Majorana pair based qubits for fault tolerant quantum computing architecture using superconducting gold surface states

A switchable Josephson junction is provided that includes a plurality of ferromagnetic insulators that are defined by their respective magnetic alignments. A first superconducting layer that is positioned between any two of the ferromagnetic insulators, wherein the conductive state is controlled by the relative magnetization orientation of the ferromagnetic insulators where the first superconducting layer is superconducting when the two magnetizations are aligned in antiparallel but it turns normally conducting when the magnetic alignment is parallel. A second superconducting layer is adjacent one of the ferromagnetic layers, wherein Josephson tunneling occurs between the first superconducting layer and second superconducting layer across one of the ferromagnetic layers.

Switchable superconducting Josephson junction device for low energy information storage and processing

A memory element is provided that includes a ferromagnetic (FM) layer having one or more ferromagnetic materials. One or more first molecule layers are positioned on the FM layer where charge transfer and interface chemistry between the one or more first molecule layers and FM layer induces a magnetic moment in the one or more first molecule layers. The magnetic moment is stored in the one or more first molecule layers acting as bit information that is retained or written into the one or more first molecule layers. One or more spin-filter layers are positioned on the one or more first molecule layers. The one or more spin-filter layers are positioned on the one or more spin-filter layers to form a physical or a chemical &#x3c0;-dimer layer structure.

High density molecular memory storage with read and write capabilities

A Josephson junction (JJ) device includes a buffered substrate comprising a first buffer layer formed on a substrate. A second buffer layer is formed on the first buffer layer. The second buffer layer includes a hexagonal compound structure. A trilayer structure is formed on the buffered substrate comprising at least two layers of a superconducting material. A thin tunnel barrier layer is positioned between the at least two layers. The buffered substrate is used to minimize lattice mismatch and interdiffusion in the trilayer structure so as to allow the JJ device to operate above 20 K.

Josephson junction device for superconductive electronics with a magnesium diboride

Ferromagnetic-insulator-ferromagnetic trilayer junctions show magnetoresistance (JMR) effects ranging from about 16% to several hundred percent at room temperature. Larger effects are observed when the actual tunneling resistance (R.sub.T) is comparable to electrode film resistance (R.sub.L) over the junction area in cross-geometry junction measurements. The geometrically enhanced large JMR can be qualitatively explained by the nonuniform current flow over the function area when R.sub.T is comparable to R.sub.L, in the cross-geometry junction structure. For a fixed junction area, the effective junction resistance (R.sub.J) can be varied from less than 1 ohm to several kilohms by controlling the thickness of the insulating layer or by appropriately selecting ferromagnetic films. The trilayer tunnel junctions of the present invention are nonvolatile, stable and are reproducible.

Tunnel junction device for storage and switching of signals

Ferromagnetic/insulator/ferromagnetic tunneling has been shown to give over 10% change in the junction resistance with H less than 100 Oe, at room temperature but decreases at high dc-bias across the junction. Using such junctions as magnetic sensors or memory elements would have several advantages; it is a trilayer device and does not strongly depend on the thickness of FM electrodes or the tunnel barrier; submicron size is possible with high junction resistance and low power dissipation. The magnitude of the effect is consistent with the simple model of spin-polarized tunneling between ferromagnets.

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Somerville, MA, United States of America

Jagadeesh S Moodera