Abstract: A method includes obtaining a plurality of entangled qubits, with high fault tolerance, represented by a lattice structure. The lattice structure includes a plurality of contiguous lattice cells. A first subset of the plurality of entangled qubits defines a first plane, and a second subset of the plurality of entangled qubits defines a second plane that is parallel to and offset from the first plane. The plurality of entangled qubits includes a defect qubit that is entangled with at least one face qubit on the first plane and at least one edge qubit on the second plane.

Abstract: A method and a device for correcting quantum state information are disclosed. A decoder receives information identifying syndrome values for a plurality of entangled qubit states represented by a graph state with a respective edge of the graph state corresponding to a respective qubit state of the plurality of entangled qubit states. The decoder repeats identifying one or more clusters of qubit states and/or syndrome states in the graph state until all of the one or more identified clusters are determined to be valid while increasing a size of a respective cluster each time the identifying operation is performed. The decoder reconstructs one or more qubit states and/or syndrome states for respective clusters; and stores information identifying the one or more reconstructed qubit states and/or syndrome states.

Abstract: A method includes receiving a plurality of quantum systems, wherein each quantum system of the plurality of quantum system includes a plurality of quantum sub-systems in an entangled state, and wherein respective quantum systems of the plurality of quantum systems are independent quantum systems that are not entangled with one another. The method further includes performing a plurality of joint measurements on different quantum sub-systems from respective ones of the plurality of quantum systems, wherein the joint measurements generate joint measurement outcome data and determining, by a decoder, a plurality of syndrome graph values based on the joint measurement outcome data.

Abstract: A device includes a plurality of first switches. Each first switch includes a set of two or more first channels. Each first switch is configured to shift photons in the set of first channels by zero or more channels, based on first configuration information provided to the first switch. The device further includes a plurality of second switches. Each second switch includes a corresponding set of two or more second channels. The plurality of second switches is coupled to two or more output channels. Each second switch is coupled, by the set of second channels, to outputs of two or more first switches. Each second switch is configured to shift photons in the set of second channels by zero or more channels, based on second configuration information provided to the second switch so that photons are provided to respective output channels of the two or more output channels.

Abstract: A method includes receiving a plurality of quantum systems, wherein each quantum system of the plurality of quantum system includes a plurality of quantum sub-systems in an entangled state, and wherein respective quantum systems of the plurality of quantum systems are independent quantum systems that are not entangled with one another. The method further includes performing a plurality of joint measurements on different quantum sub-systems from respective ones of the plurality of quantum systems, wherein the joint measurements generate joint measurement outcome data and determining, by a decoder, a plurality of syndrome graph values based on the joint measurement outcome data.

Abstract: A method includes receiving a plurality of quantum systems, wherein each quantum system of the plurality of quantum system includes a plurality of quantum sub-systems in an entangled state, and wherein respective quantum systems of the plurality of quantum systems are independent quantum systems that are not entangled with one another. The method further includes performing a plurality of joint measurements on different quantum sub-systems from respective ones of the plurality of quantum systems, wherein the joint measurements generate joint measurement outcome data and determining, by a decoder, a plurality of syndrome graph values based on the joint measurement outcome data.

Abstract: A device (e.g., a photonic multiplexer) is provided that includes a plurality of first switches. Each first switch in the plurality of first switches includes a plurality of first channels. Each first switch is configured to shift photons in the plurality of first channels by zero or more channels, based on first configuration information provided to the first switch. The device further includes a plurality of second switches Each second switch includes a plurality of second channels. Each second channel is coupled with a respective first channel from a distinct first switch of the plurality of first switches. Each second switch is configured to shift photons in the plurality of second channels by zero or more channels, based on second configuration information provided to the second switch.

Abstract: A method includes obtaining a plurality of entangled qubits, with high fault tolerance, represented by a lattice structure. The lattice structure includes a plurality of contiguous lattice cells. A first subset of the plurality of entangled qubits defines a first plane, and a second subset of the plurality of entangled qubits defines a second plane that is parallel to and offset from the first plane. The plurality of entangled qubits includes a defect qubit that is entangled with at least one face qubit on the first plane and at least one edge qubit on the second plane.

Abstract: A quantum computing system and methods for performing fusion based quantum computing on encoded qubits. A fusion controller sequentially performs a series of fusion measurements on respective photonic quantum modes of first and second encoded qubits to obtain a respective series of classical measurement results. For respective fusion measurements of the series of fusion measurements, a basis for performing the respective fusion measurement is selected based on classical measurement results of previous fusion measurements. An encoded fusion measurement result is determined based on the classical measurement results, and the encoded fusion measurement result is stored in a memory medium.

Abstract: Entanglement among qubits can be generated using “rasterized” and interleaving techniques. A circuit can include a resource state generator that generates one resource state per clock cycle, with each resource state having a number of entangled qubits. The circuit can also include circuits and delay lines to perform entangling measurement operations on qubits of resource states generated by the same resource state generator in different clock cycles. With appropriate selection of delay lines, a single resource state generator can generate all of the resource states needed to generate a large entanglement structure. Hybrid techniques can also be used, where the number of resource state circuits is greater than one but less than the number of resource states needed to generate the entanglement structure.

Abstract: A quantum computing system and methods for performing fusion based quantum computing on encoded qubits. A fusion controller sequentially performs a series of fusion measurements on respective physical qubits of first and second encoded qubits to obtain a respective series of classical measurement results. For respective fusion measurements of the series of fusion measurements, a basis for performing the respective fusion measurement is selected based on classical measurement results of previous fusion measurements. An encoded fusion measurement result is determined based on the classical measurement results, and the encoded fusion measurement result is stored in a memory medium.

Abstract: A device includes a plurality of photon sources coupled to a plurality of output terminals. The plurality of photon sources are coupled together, by a first switch layer, into a plurality of photon source groups. The first switch layer comprises a plurality of switches. The device further includes a second switch layer coupled to output terminals of the first switch layer. The second switch layer includes a plurality of second layer n-by-n switches and a plurality of second layer l-by-l switches, wherein l is less than n. At least two output terminals from two respective photon sources residing within a first photon source group of the plurality of photon source groups and a second photon source group of the plurality of photon source groups are coupled directly to respective output terminals of the device without being coupled to any intervening second switch from the second switch layer.

Abstract: A method and a device for correcting quantum state information are disclosed. A decoder receives information identifying syndrome values for a plurality of entangled qubit states represented by a graph state with a respective edge of the graph state corresponding to a respective qubit state of the plurality of entangled qubit states. The decoder repeats identifying one or more clusters of qubit states and/or syndrome states in the graph state until all of the one or more identified clusters are determined to be valid while increasing a size of a respective cluster each time the identifying operation is performed. The decoder reconstructs one or more qubit states and/or syndrome states for respective clusters; and stores information identifying the one or more reconstructed qubit states and/or syndrome states.

Abstract: A device (e.g., a photonic multiplexer) is provided that includes a plurality of first switches. Each first switch in the plurality of first switches includes a plurality of first channels. Each first switch is configured to shift photons in the plurality of first channels by zero or more channels, based on first configuration information provided to the first switch. The device further includes a plurality of second switches. Each second switch includes a plurality of second channels. Each second channel is coupled with a respective first channel from a distinct first switch of the plurality of first switches. Each second switch is configured to shift photons in the plurality of second channels by zero or more channels, based on second configuration information provided to the second switch.

Abstract: A quantum computing system and methods for performing fusion based quantum computing on encoded qubits. A fusion controller sequentially performs a series of fusion measurements on respective physical qubits of first and second encoded qubits to obtain a respective series of classical measurement results. For respective fusion measurements of the series of fusion measurements, a basis for performing the respective fusion measurement is selected based on classical measurement results of previous fusion measurements. An encoded fusion measurement result is determined based on the classical measurement results, and the encoded fusion measurement result is stored in a memory medium.

Abstract: A method includes receiving a plurality of quantum systems, wherein each quantum system of the plurality of quantum system includes a plurality of quantum sub-systems in an entangled state, and wherein respective quantum systems of the plurality of quantum systems are independent quantum systems that are not entangled with one another. The method further includes performing a plurality of joint measurements on different quantum sub-systems from respective ones of the plurality of quantum systems, wherein the joint measurements generate joint measurement outcome data and determining, by a decoder, a plurality of syndrome graph values based on the joint measurement outcome data.

Abstract: A device includes a plurality of photon sources coupled to a plurality of output terminals. The plurality of photon sources are coupled together, by a first switch layer, into a plurality of photon source groups. The first switch layer comprises a plurality of switches. The device further includes a second switch layer coupled to output terminals of the first switch layer. The second switch layer includes a plurality of second layer n-by-n switches and a plurality of second layer l-by-l switches, wherein l is less than n. At least two output terminals from two respective photon sources residing within a first photon source group of the plurality of photon source groups and a second photon source group of the plurality of photon source groups are coupled directly to respective output terminals of the device without being coupled to any intervening second switch from the second switch layer.

Abstract: A method and a device for correcting quantum state information are disclosed. A decoder receives information identifying syndrome values for a plurality of entangled qubit states represented by a graph state with a respective edge of the graph state corresponding to a respective qubit state of the plurality of entangled qubit states. The decoder repeats identifying one or more clusters of qubit states and/or syndrome states in the graph state until all of the one or more identified clusters are determined to be valid while increasing a size of a respective cluster each time the identifying operation is performed. The decoder reconstructs one or more qubit states and/or syndrome states for respective clusters; and stores information identifying the one or more reconstructed qubit states and/or syndrome states.

Abstract: A method includes obtaining a first qubit entangled with second, third, fourth, fifth, sixth, and seventh qubits and one or more of: an eighth qubit entangled with the second qubit and the seventh qubit; a ninth qubit entangled with the third qubit and the fourth qubit; a tenth qubit entangled with the fifth qubit and the sixth qubit; an eleventh qubit entangled with the eighth qubit and the ninth qubit; a twelfth qubit entangled with the eighth qubit and the ninth qubit; a thirteenth qubit entangled with the eighth qubit and the tenth qubit; a fourteenth qubit entangled with the eighth qubit and the tenth qubit; a fifteenth qubit entangled with the ninth qubit and the tenth qubit; and a sixteenth qubit entangled with the ninth qubit and the tenth qubit. Also disclosed are additional methods of obtaining a plurality of entangled qubits.

Abstract: A method for obtaining a plurality of entangled qubits represented by a lattice structure that includes a plurality of contiguous lattice cells. A respective edge of a respective lattice cell corresponds to one or more edge qubits, and a respective face of the respective lattice cell corresponding to one or more face qubits. Each face qubit is entangled with adjacent edge qubits. A first face of the respective lattice cell corresponds to two or more face qubits, and/or a first edge corresponds to two or more edge qubits. A device for obtaining the plurality of entangled qubits represented by the above-described lattice structure is also described.